While I agree with the thread title (and am glad to find a thread devoted to the idea for once rather than the barrage of contrary ones), I'm not entirely in agreement with the reasoning of the OP.
People have listed a lot of reasons why they want the Inquisitor to be the protagonist in the next DA game. Here, I'm going to list the reasons why I do NOT want that. Basically, it comes down to this: the Inquisitor carries too much ballast around to work for me as a new protagonist. Here is why:
(1) A clean cut with Southern Thedas
I'm sick of southern Thedas and its problems. I'm sick of the Circles, the Orlesian Chantry, mages vs. templars and Orlesian Andrastianism. I was looking forward to playing in Tevinter, playing a native Tevinter citizen, encountering new people from there and immersing myself into a new culture. I want to leave southern Thedas behind as far as possible, and playing as the Ex-Inquisitor would be like a heavy chain binding me to everything I want to leave behind,
(2) Trespasser's ending makes for a lot of ballast I don't want.
I was happy after the ending of the game, before Trespasser. I like my Inquisitors, but I was quite happy to leave them behind as leaders of the Inquisition. It was the first ending of a Bioware game that I found unreservedly satisfying since DAO. Then came Trespasser and ruined everything, and now I'm considerably less happy. I'm quite prepared to start as a character with a low power level in DA4, but for an old protagonist to be hammered down, taking away everything they have gained and more, in order to make them feasible, that would be like a slap in the face by the writers. I do not like to be slapped in the face, and I'd rather not start the next DA game being angry. I'd rather start with the kind of pleasant anticipation I had with DAI. Playing the Ex-Inquisitor would make that impossible.
(3) Trespasser has weakened my connection to the Inquisitor
People have said Trespasser made the Inquisitor more relatable. This term may be important to a story you watch and read, but less to a roleplaying game. I guess some people experience Bioware's games as more of stories they watch than shape, and perhaps with some justification. I'm a roleplayer, however. I do not "relate" to my character, I automatically have a much closer connection to them than that, and I'm automatically invested in them as long as the writers don't put words into their mouths I would never have them say, or make them do things I'd never make them do. That almost never happened in DAI, and so my Inquisitor has been, right from the start, one of three Bioware protagonists I could connect to with no problem at all (the others are the Bhaalspawn and the Warden). Bioware's writers are the GM to me.
Now imagine if in a tabletop RPG campaign, your GM did to your character what was done to the Inquisitor with no input at all from you. I don't know about others, but in that situation, I consider it very likely I'd say "Not with me, I'll make a new character". In that way, Trespasser made the Inquisitor less my character - and thus less "relatable" as the protagonist of a game - than she had been before, and it would be an uphill battle to remake the connection. Again, I'd rather start the game without that kind of ballast.
So...I do NOT want the Ex-Inquisitor to be DA4's protagonist. I'm not saything such a setup couldn't be a success, but I rather suspect that Bioware's writers won't do any of the things that would make it palatable to me.
1. I like Southern Thedas. I do want to experience the rest of Thedas- even "those across the sea" that were hinted at, since the landmass we've seen so far may just be one/two continents on the planet. But I'm in no way averse to revisiting old areas and would rather they continue to incorporate everything. That seemed one of the strengths of DAI- not abandoning Ferelden just to bring us to Orlay. That's one of the excellent experiences that DA tends to offer- the "return" visits. I'd love to be back in Orzammar again especially... which is in southern (known) Thedas. Gotta wonder if the vast dwarven underground of ancient times extended under the sea to other continents as well...
And the various themes of Chantry/Orlesian politics/mage-templars... are sorta canon DA by now. I just want a better experience with them than a little Hinterlands scuffle. Even DAO did more with the Redcliffe narrative than DAI did with the entire Hinterlands.
2. I also enjoyed the ending of Trespasser... though it was a tad aggravating having ploughed through all those qunari only to find Solly having been able to one-shot every single one of the nasties I'd spent so much time and effort killing as if to save him. The main thing is that narratively it was pretty cool and leaves me interested in how Solas will be approached in DA4 and what will be available to be done about him and whatever plans he may have. This in no way requires the Inq returning, however. The Trespasser end just opens up DA lore and historical development interestingly.
3. The point is not really made by saying only that the Inq is "unrelatable." Without a strong DAO-like origin pre-story, the Inq is already seriously lacking in "relatability," but that's not the point made. I like better what you said in this same regard later in the thread:
Unfortunately, my disaffection exists on the meta-level and it has no in-world outlet. My Inquisitor would be not so much mad at Solas as mad at the vagaries of a cruel fate that brought her to this point - or maybe at the Maker, but she doesn't believe in him. Solas threatens the world as we know it, but he isn't responsible for her losing her arm, the Anchor and most of her political power. So in terms of making things personal with regard to Solas' plans, Trespasser was a complete failure, because the motivation I can relate to most closely at the moment, on an emotional level, is rather more of a villain's: "**** the world, I'm going to take back what was mine". Well, if I could play *that* out, it might actually work, but Bioware's games don't facilitate it as a rule.
The only Inquisitor who would work, apart from that, is one who romanced Solas.
It is entirely possible to play DAI without even traveling with Solas, not doing his artifact quest or anything else- or even playing an Inq completely at odds with Solas. This hardly leaves one with a personal score to settle with Solas. It's more just a matter of another mess that needs to be cleaned up, Solas just the messer-upper (no less than Cory with whom no personal investment occurs either) rather than some close friend/ex-lover/acquaintance to be dealt with. This makes an emotional Inq-Solas relationship non-canon. That some may have some emotional investment in the undoing of Solas' plans does not negate the fact that a different DAI playthrough will involve zero such investment. Not that emotional investment by a protagonist's journey automatically requires that the protagonist return either. There is a strong case (that I've made in the pro-Inq-return threads) for a potentially greater emotional narrative with a new protagonist that experiences more canon encounters with Solas.
Not to mention the fact that the successful invasion of Tevinter by the Qunari- as mentioned in Trespasser's end as well- is hardly a secondary concern. Solas is just one patch of DA4's mosaic of potential challenges to face...
What gets left out or poorly rebutted in the case for a new protagonist (or perhaps rather in the case against a returning Inq protagonist) are these technical considerations:
1. How to CC the DAI Inq in DA4.
The new DA will likely have yet another game engine advancement. There's plenty more to add to DA, including shifting hair, among plenty more upgrades. Unless we keep the same game engine (already not as advanced as a number of others contemporary with DAI), we'll have to recreate our Inq again. Many probably couldn't care less, but I'm one of those that gets wed to a particular appearance (sculpted from hours of CC work) for my protag. There's no way to reproduce them exactly the same, so they won't be the exactly the same Inq in a DA4. I can live with it if the Inq is an NPC like Hawke was in DAI (though I admit I didn't like that either), but not if I'm running with them again as the protag I'd forged in DAI. I'm betting that they'd have no way to be able to lift the exact appearance graphs from DAI to reintegrate them perfectly in a new engine for DA4. Hell, they'd have to have the same (limited) hairstyles, skin textures, hair and eye colors, etc.- and all in the same format as DAI. Is it not easier to just, ya know, make it a new protag with the new CC?
2. The drop to Lvl 1.
They could make DA4 like BG2 where you start with the level you left off from (or simply a set higher level)... It's just highly improbable. They would have to scale every encounter from the get-go to that higher level. This is not a consideration in an FPS game in which you never "level up" and only just acquire better weapons throughout the course of the game- your skills increasing simply because you, as the player, get better at it. DA isn't an FPS. And, as we've seen, they keep changing the ability/spell tree system around for every new game, so coming back with the same character requires a break with that same game concept. On the one hand, DAI's combat had severe limitations (the 8-quickslot one being just one), so we'd have to see a return of that same combat experience in order to have the Inq continue as they were. If they come up with yet another new set of advancement abilities, the cognitive dissonance of advancing with a different system using the same character is just glaring. The tendency to balk would be universal. They can't win either way if they use the Inq again. They can win either way with a new protag.
But then there's the simple fact of explaining how a (potentially) Lvl27 character is now Lvl1. One attempt at a contrivance I read was that the missing arm forces the Inq to start over. Yeah... but starting over doesn't mean starting from absolute scratch. We still retain the same abilities, even if we're now unable to execute them. Or would we really lose all that magic-casting knowledge just because we're short an arm? Would you forget how to write just because you broke your writing hand? No, the missing arm doesn't serve to explain the contrivance. It's a comprehensive loss of everything you'd gained skill-wise. Could the writers come up with a DA4 story that involves the Inq being mind-wiped so that they can't recall their former abilities? Yes, they could. But then we wouldn't exactly have the same Inq's, now would we? Part of the Inq's identity was the skill development they'd acquired after that many hours playing DAI. And normally when memory is wiped you get a "Jason Bourne" type of amnesia where they don't know who they are but they retain their skills. That would eliminate the whole "but I gotta play my Inq because they have a relationship with Solas (that now they can't remember)," and the reverse scenario where a person remembers their identity but not their skills doesn't tend to be the rule. As they say, "Your skills are something no one can take from you." Unless the writers pull a narrative from their arses. But all this trouble to contrive a Lvl1 nerfing when the writers could instead just create new protags?
Then there's the protest of "Yeah, but they did the same with Varric!" To which I say: "Exactly." I seriously dislike what they did there, making him return as a Lvl1 companion after all the hours I'd spent with him, never leaving my Champion's side, bringing him and Bianca to Lvl 25 or so in DA2. And I like Varric as a character and companion. I just don't like seeing him gutted in order to bring him back. I'd rather have had a new dwarven companion (or two or three or four) that made sense to start at Lvl1 with. I'm getting around the dissonance of Blanca being now less powerful than anything I can craft (despite the Skyhold note forbidding Varric from participating in archery contests due to how uber-skilled he's supposed to be) by making him a dual wield rogue instead. Alas this still doesn't explain why he isn't starting at Lvl 25 or unable to be respecced to that level. So the absurdity remains.
The other possibility is that they could have DA4 be a "high-level adventure." This would mean creating a new world where the level-cap of DAI at Lvl27 doesn't/didn't exist and is instead, say, Lvl50. Now bears and Sha-Brytol warriors and demons and Vint mages, etc., could suddenly be Lvl 48- something they've never been before. The devs could do it, but that would take a completely new rethinking of the gameplay of DA which has more or less been Lvl1-25 for three games now. And what about players who finish the main game in DAI less than Lvl 20? I always work to get the max lvl by the end of the game, but others don't. So where do they start in DA4? Lvl20 for my Lvl27 Inq? Lvl27 for their Lvl20 Inq? All these questions aren't just for the "bring back the Inq as protag" crowd. It's what that same crowd is asking the devs to wrangle with. And all along a new protag just makes this an elegantly simple matter: start at Lvl1 with a new protag.
3. The Inq's relationships/experiences.
Another thing that only makes the writers' job more difficult would be attempting to factor in all the various ways that DAI had been played into the narrative of DA4. Every bit that they're forced to write in in order to reintroduce the Inq entails a disinvestment in providing new content. And there's a boatload they'd have to factor in. They'd have to bring back Leliana as the potential spymaster that we know, LI's as somehow involved in the Inq's life, encounters with the myriad NPCs and narratives in DAI, etc., etc., all things they'd have to create workarounds for or incorporate into DA4's plot development that they could pretty much sail through using a new protag. Did I enjoy immensely the fan service they added from DAO and DA2 to DAI with returning characters and references to events past? Yes! Entirely! But none of those needed to be part of the basis of the game. That my Warden had romanced Leliana in DAO (according to my Keep story anyway) showed up in DAI as a nice side-story, but that my Inq romanced Blackwall would now not be a side-story at all- and if it were treated as such with my DA4 Inq protag it'd be disappointing for those wanting a return of the Inq as protag (which I'm not). As DAI experiences they were referential, incidental, colorful- but not essential. Whether your Warden had a relationship with Leliana or Morrigan was just something fun to discover the results of, not something the writers had to devote substantive portions of DAI explaining and working in. If the Inq is back as protag they'd have to revisit all of that, reincorporate them all, account for them all as they applied- or even as they didn't apply (and why)- to the rollout of DA4's plotline. With a new protag such harkenings are just fun and the DA4 plot meanwhile can rollout unhindered (other than by consistency with DA's lore generally).
4. High-level equipment loss.
So much for all that schematics grinding, the Golden Nug, and favorite crafting that your Inq struggled through. BG2 had a narrative that explained how you ended up losing nearly all your good gear from BG1- i.e., having been abducted and experimented upon by Irenicus. (In the upcoming "Dragonspear" game that will bridge BG1 and BG2 apparently you'll be keeping your equipment, but, you see, that's BG. It involves a single protagonist navigating multiple game installments keeping the same abilities and more or less the same cast of characters (BGEE adds a few more), so keeping your equipment works.) DA continues to make it obvious why your new protag needs new equipment: they're starting new in the changing DA narrative landscape and are taking what they can get. With the Inq what possible reason is there that the gutted Inquisition- or its allies- like whoever you made Divine- can't continue to supply you with all you had in DAI? What could possibly pry that Hakkon's Wrath bow from your Inq's cold, dead archer hands? Could some reason be contrived? Yes- absolutely. But it would have to be contrived. There's no contrivance necessary with a new protag: new stuff comes with the territory.
And just like the skill tree system, they'd have to bring back all those items that the Inq might've encountered. Who knows which remains in regular use by the Inq or was stored in the Storage Chest? Again, if they invest in that sort of continuity they automatically disinvest in new content.
5. The missing arm.
I've seen plenty of interest in playing as a handicapped person... who nevertheless has perfect use of a new arm. The thing is, either they can restore the arm entirely- in which case no loss of abilities occurs and the loss of the arm was meaningless and inconsequential (since it's not really lost after all, now is it?)- or they can make you remain one-armed or deficient in some way- in which case they'd have to rework a huge number of two-handed skills in DA4 to accommodate that. The former loses all the sentimental aspect of playing "handicapped" since effectively you wouldn't be handicapped, and the latter requires yet another round of cognitive dissonance when you're equally effective with only one arm. What skills aren't two-handed in DA? Sword-shield, DW rogue, archery, 2H weapons, staves... Why would they bother tweaking all the abilities and animations just to reintroduce the Inq? I'd rather the gameplay development folks concentrate on making a more fun combat and tactics system for new protags rather than trying to figure out how to portray the same mechanics now able to work (somehow) for a one-handed Inq. And again: a new protag with all limbs intact is simply simpler.
6. DA tradition of new protags.
This may seem more a narrative concern than technical, but it is incontrovertible that DA has always involved a new protag facing a new situation that called for a new type of hero. This is a gameplay question as well. They'd have to restructure their entire approach to DA in order to make a recurring protagonist- both narratively and mechanically. And it wouldn't exactly be revolutionary: most games have a set protagonist that carries through to each new installment (Elder Scrolls being the other notable exception). DA is one of the precious few major franchises that explores the multi-race, new-protag formula. They implemented it profoundly in DAO, winning a huge following to the franchise, and they scored big with the same formula in DAI with all the GOTY accolades. New protags has been a fundamental DA game mechanic. Thus the argument to bring back the Inq is an argument to destroy that mechanic and make DA just like other rpgs in that respect. If some have lost faith in the "new protag" formula (even if only "because of Trespasser" as the rationale), there are plenty of others like myself that haven't. I love starting from scratch with someone(s) new every time. I'm very happy they didn't try to bring (meh) Hawke back as the Inq or bring back my beloved DAO Wardens for DA2 (though, yeah, humans-only in DA2 was disheartening). They didn't make the Inq's origins in the least endearing, but I'd rather have had that than a contrived return of former protagonists. And nothing in the "Me want Inqui back" arguments makes me feel like seeing DA abandon its foundation. I can see all the same drama and narrative development with a new protag for DA4- Solas' unfinished business, the Inq's declared (not realized) intent to do something about it, and all.
Mike Laidlaw made a more elegant argument for the "new protag" formula in some interview I read a while back, but still...
So, yeah, the devs could come up with a new DA- one with a returning protag- but they'd have to break the nature of DA and expend resources to retroactively explain a Lvl1, equipment-starved, one-armed, DAI-uninvolved, different-looking Inq. Why... why would they bother? It's not as if the "new protag" formula has failed or would fail in DA4. There would be no more loss than in jettisoning Hawke or the Warden as protag in a wide open new DA to introduce us to... Just let it go and enjoy the new protagonist options of DA4 as to how you resolve the next round of DA lore and antagonists. (Watch them make the new protags be all human variants just to try my patience anyway...)