The only way that I will ever be happy with seeing an old PC reappear in a new game is if they are, again, a PC. Adding a voice to a previously unvoiced character would just make it worse, since that would add another level of lack of control.
What they did in DA:I actually worked very well for me. I am completely fine with that kind of mention, and that level of reference. It would've been nice to add something to the Keep such as "what goal was most important to them" or some such under the DA:O section, since I realise that what they were said to be doing wouldn't work well for every character, but overall I think it was the right way to handle it.
I'd also be okay with never seeing or hearing from the character again. Far better that then end up with some weird doppleganger shambling around taking their place, since we can't control them.
I really believe that the best way to handle a future appearance of
any previous PC would be to have a sub-section where you play as that character, or even take turns playing as both that character and your current character in the same section (not impossible; one was frequently able to choose which character would speak to an NPC and so forth in older games -- indeed, one could even flash from you picking one response to you picking another response in a conversation, although that'd be trickier to plot out). I'd say that the only way to be completely respectful of everybody's choices about their characters, and yet have them show up again, is to let them play them again as well. Otherwise, it is best to stick to references.
Oh I don't know, maybe because characters having voices is what happens nowadays? Yes it is my problem, however Bioware gave me the solution by providing voices back in DA 2 so nice try 
"What happens nowadays" does not work as a valid basis for an argument that centers around personal preferences. If you go back in time a decade, that very same argument would apply to un-voiced characters. If you go back more than twenty years, it could apply to games being largely text-based. The current trend is always changing, and the fact that something is the current trend gives it no more or less inherent worth.
"How you role play it"..In other words, "my warden only has a personality when I play pretend." That may work for you but that doesn't work for everyone else.
That is the general premise of a roleplaying game, yes. I'm aware that roleplaying games have always been something of a niche genre, and so I'll not argue that it doesn't work for many people, but Dragon Age is still (at least for now) a roleplaying game franchise. The ability to roleplay one's character must be kept.
Many people are also able to successfully roleplay a character who is voiced. I find it to be a struggle, but can do so, although it severely limits the replayability of the game in question (as each voice becomes associated to one character for me), and causes frustrations in the form of the uncertainty created by the paraphrase system. I'm much happier with an unvoiced protagonist.
A majority of the dialogue lines you could pick from in Origins were irrelevant because the NPC would wind up saying the same thing regardless. The only difference was in how you said it.
The same is true of all roleplaying games, or at least, all BioWare games that I can think of. Since they are roleplaying games, shaping and demonstrating your character's personality via the things they say (and, ideally, how they say them) is hardly irrelevant. Yes, they often lead to the same line said by the NPC. That's no different in Mass Effect, or in DA II, or in DA:I.
The game that I can think of with the most varied dialogue and responses by NPCs to said dialogue is
Planescape: Torment. That wasn't voiced. The depth and responsiveness of the dialogue system does not hinge on a voiced protagonist or a lack thereof; it is writing and design.
See you already went through the process of picking a voice. Now imagine if they had that voice and actually spoke their lines. That's a whole lot better than sitting there and "role playing", smh" what they sound like. This is a video game, not a book.
It's a computer
roleplaying game, not an interactive film.
If they bring the Wardens back, which you're actually in the minority since I see plenty wanting the Warden to return in the other forums, then it would be redudant for them to be silent when everyone else is talking.
I don't think redundant is the word you're looking for there (maybe strange?), but there are also plenty of people who don't want to see that, especially with how the Champion's return was handled in DA:I. Even many people who like voiced PCs aren't very fond of not being able to control what their old PC is doing, at all.
If you're controlling the character again, it wouldn't be strange. If you're not, I for one certainly don't want to see the character at all.
It'd be like Bioware taking a step back just to appease to those who enjoy the silent protagonist when things are different now.
Since, arguably, putting in a reappearance of the Warden would be designed to appease -- or at least play to -- the people who like DA:O to begin with, perhaps they would prefer to do so in a manner that those same people would actually enjoy (if at all)?
Also, not a step back. It is simply a different way of doing things, with its own advantages and disadvantages. I personally feel that the advantages of having an unvoiced PC far outway the disadvantages, but that is entirely a matter of opinion. There is no objective answer on it. The closest thing to an objective answer you're going to get there is that a voiced PC takes more resources, which would tend to swing the balance in favour of the unvoiced PC, if anything.
Hawke was pefectly fine until they had him do that bit about the Wardens. If I didn't say it before, that's hardly a reason why he or the warden shouldn't be included. Like I said, that was probably just a poor way for them to have had someone to disagree with Stroud/whoever.
For you. Not for everyone. For me, there were a few problems there, and I know some other people who had a lot more personality-clash issues with the choices they made for the Champion there.
It would be much worse with the Warden. There isn't even the dubious characterisation shortcut of the Aggressive/Sarcastic/Diplomatic personality trend for them to use, although I suppose one such could be added.