Oh thank the Maker it was all still under auto-saved content. Okay, NOW here we go. NOT spoilered for length because that screwed it up last time. (So sorry for everyone not interested in my pessimistic rambling)
Whew! Finally back. Okay, onto this now...
The thing with Solas is part of him knows his plan is not a good plan and that he is wrong but it's such a wrought, complicated decision that, for reasons, he feels resigned to. Different if he doesnt like you, but if he's a friend or romanced, there's room in what he says and his body language that he's not 100% committed and would welcome the chance to be proven wrong again and/or stopped.
I think it was a friend Inquisitor who chooses to try and redeem him that he says that he welcomes the chance for you to prove him wrong again. IIRC - correct me if wrong, someone.
I agree, but it makes me wonder why he's resigned to it. Part of the end of Trespasser reminds me of the early game conversation you can have about a world without a Veil, and it's basically a rehash of that. And I remember being frustrated then too, that the game directs you into sharing your opinion about the idea when you're really given no information on it. All Solas really says is "It could be dangerous, but also helpful." Well that's bloody great - but how? Why? What are the pros, what are the cons, how can it be achieved? It would've made sense if it let you ask only for Solas to just give some blithe non-answer because he can't reveal that much, but even that option's not present. I don't want to just blindly agree because I'm gaming approval, and I don't just want to shoot the idea down then and there because it sounds like it could be a disaster, but those are really the only options it gives, when I just want to say "Well, I need a little more info to come to any meaningful conclusion."
It's the same here. I don't know enough to say that's an evil jerk, but I don't know enough to say that he's a tragic martyr either. I need a little more info to come to any meaningful conclusion.
I guess that's basically what I'm trying to get at.
I don't have a lot to add but I have this feeling that they have something much bigger planned for him. We've had so many assurances that he truly cares about people that there just -has- to be more to it than, "Well, now I'm a villain with no redeemable qualities." He cares. His plan doesn't look good from our point of view but I believe that's only because we haven't seen it from his. I really hope we get to see him in action in DA4 and get to know what he's up to and why he feels this is the only choice he has. I also think the developers are starting to understand their audience better and they know this is a huge tease and it's going to be amazing if/when all of this is revealed. I was happy with how Trespasser went even though it left me confused and baffled and wanting DA4 more than ever. 
I agree here, too - they've definitely got something bigger in store for Solas. But what concerns me is that bigger, as they say, is not always better. It's not out of the question that whatever's revealed paints an even worse picture of our dear egg.
I want to think that he's kind and he cares. But there comes a point where, no matter how often the writers tells us that, even if they use the other characters to say it, there comes a point where they've got to show it too. And they do, sometimes - but sometimes they show a Solas who's cold and callous and apathetic to others' suffering. There's the Dalish, for one example. Qun!Bull, for another. He's not exactly kind to either, despite both having pain of their own. He can be so contradictory. And I wonder sometimes if that's my fault, because I obviously like him and tend towards a more charitable view, which can cause me to gloss over his uglier aspects. So I try to combat the tunnel vision by seeking out the negative opinions of his character, and the explanations end up seeming so at odds.
I don't really see reason why they shouldn't intentionally hide better parts in easy-to-miss places - I quite like that aspect of the game. It's subtle, requires attention to detail and open-mindedness, so I'll always prefer that to giving us big red arrows or shouting from the heavens "he's not a bad guy! Really, he isn't! There's more merit to his plans that we actually reveal now!!" (although Cole in Trespasser was kinda pushing it
"He's not that kind of wolf!" "The arrow breaks in sad wolf's jaws" Yes Cole! I get it!!).
Therefore no, I don't see Solas's character as not coming through exactly how they wanted him to. They've already revealed that one of reasons they let him romance only female elves is because they don't want the audience to categorize his behavior under a bad bi trope - because they knew how many people would see him.
I suppose my issue with hiding things in out-of-the-way places, especially with major aspects of even more major character, is that it's so easy to see things that aren't even there. Like, you can only dig so deep before you've got to ask yourself "Is this actually supported by the text or am I just seeing what I want to see?" I don't want to over-idealize a character only to be blindsided by their faults - which is basically what happened with Trespasser. I remember, after it was announced but before it came out, I had this talk with a friend and I said "There's no way they'll just have Solas waltz in at the end, hack off the Inquisitor's arm, cackle about his evil plot to destroy the world, and then exit stage left." Man, that made for one awkward post-Trespasser conversation.
As for Weekes Depraved Bisexual comment - it does give me hope that he's more aware than his "We wanted it to be clear that Solas cares about everyone" remark would suggest. But really, hope only goes so far, and like I've said, I've been disappointed by too many writers in the past to go on hope alone.
Not to mention that, if he knew people would see Solas as depraved and evil and did nothing to prevent that, well, it doesn't exactly assuage my fear that those of us who still like him are unexpected anomalies.
So it seems to me that they actually wanted to give the general audience something of an imbalanced picture - are they just going to see the bad and seek out to destroy him? Or are they going to look under the surface and mine out a more complete picture that will later inform their choices?
They did this already, on smaller scale, be it with Blackwall or Iron Bull (and on some levels with Flemeth. I've seen quite a few people after revelations in DAI and post-credit scene saying that they regret killing her in DAO)... Why shouldn't they do the same thing with Solas?
IMO they know what they want to achieve through him and it's not "a misguided guy with a really stupid plan". There's a lot we yet don't know about what's going to happen - but we do know that there are other things lurking in dark corners: the Blight's not yet done with, the Evanuris are apparently searching their way to be released, the magical races are dying out and the magic is diminishing. So there's more there that's happening that we yet see, be it when it comes to dangers to Thedas or Solas and his plans to restore the world of the elves.
I've wondered myself if that's where they're going. If they're intentionally trying to trick people into thinking he's an irredeemable villain, so that they can surprise them later. I hope that's the case, but there's that thing about hope again.
Also - I'd like to point out something: Solas doesn't seem to mourn their lost civilization as much as the lost conscious connection of people to the Fade. All people. He seems to be unable to forgive himself that he's almost Tranquilized the world and he laments the fact that the Veil took everything from the elves - even themselves.
What EXACTLY these words mean we'll likely yet find out, but I think assuming that his plan has anything to do with restoring Elvenhan to its glory and release/reform a society of True Elves is nothing more than an uncharitable misinterpretation.
While he mourns all the knowledge and marvels lost, he wasn't squeamish about sacrificing Elvenhan when he created the Veil - so I don't see reason why he should care predominantly about it now. What seems to matter to him is restore the world how it previously was - likely restore all people's connection to the Fade, which will necessarily change the world on a fundamental level.
Oh yeah, I don't think Solas wants to bring back Elvhenan either. Really, even with my pessimisstic outlook, some of the comments made about Solas are just like... Did we play the same game? Are we talking about the same character here? Like, I know Solas makes some untoward comments about humans and Qunari, but nothing about him suggested to me that he wants to wipe them from existence, or bring elves back to the top, and I mean, hell, he's not exactly all sunshine and rainbows when he talks about Elvhenan either. I figured it's obvious that it's the magic and spirits and immortality he wants back. He's no trying to restore Elvhenan. He's certainly not trying to restore Elvhenan precisely as it was, complete with eternal slavery and rampant murder and abusive god-kings. I don't know how people arrive at that conclusion.
I was just trying to cover the gamut of all the theories I've seen on him, even the ones I highly disagree with.
I also think that Solas thinks that there's another way, but the chances of that solution succeeding are minimal - unless Inquisitor actually does stuff that will prove him wrong and help him regain trust in people to help him save as much of the world as possible. This is likely why we have the redeem option in the first place - he's leaving the door open to help us convince him that that other way is worth its tremendous risk.
In any case - we're yet to find out. I expect DA4 will be all about finding out the details of his plans or more reasons for his actions, or what other dangers are there to the world... which is also likely a very big reason why many of Solas's statements are so vague; they can't really spoil the next game before it's even greenlit 
...I probably sound like I'm on the brink of hating him, don't I? Probably shouldn't have abused the phrase "evil dick" so much. But for the record - I'm not. I don't think I could ever hate him. I don't think I've ever hated any character, especially not for moral reasons, and especially not one I like as much as this jerkface. I think it's better to say that my understanding of his character is on the brink of falling into two radically different camps, and I while I'll probably still like him either way, I'd definitely prefer one over the other.
That and I was trying to explain why some people might think what they think about Solas. So I was trying to channel every opinion and reaction to him, not just the favorable ones, and not just my own.