I like a bit of heartbreak, some mystery and I like to work for the relationship. But what I don't like is feeling like I am being strung along by the occasional breadcrumb of 'I do care about you' Solas. Plus, I will never be certain of his motivation. With Solas I do not doubt he has feelings for Lavellan but I also do not doubt that she is also a tool especially in the beginning. I think being lied to repeatedly is not a great basis for any relationship, and if it were real life, it's not something I'd wish on any one. So looking at this as a game, sure I find Solas intriguing, but for whatever reason, I simply do not care about him any longer because it's all to much effort and a bit of a mind f*ck. You never know where you stand with that guy and you never know what he has planned, and it sure the hell isn't about you. It's all about him. That's okay to a point. But then it becomes too much and you can't reconcile it all and then you simply do not trust. I need some closure, something less tragic, something that gets all my emotions going but ends up worth it in the end. Solas just p*sses me off now to be honest. I see him and I want to slap him. I get that Solas really makes some people happy. I get it. But I'm on a diet. I can't handle anymore ice cream induced romances, thank you very much.
I need something more mature because I'm old. Abelas is like the all grown up Solas with benefits (thighs). He looks good in the armor and that voice... Abelas has so much potential. Hopefully it will get put to good use and I can think of so many uses for it.
I don't see either Solas or Abelas as necessarily more mature romances. It does depend in no small part on how you look at them and approach them, especially as Abelas is, at this point, largely headcanon (thus there may be wrong ways to view him that are clearly not in character, but there's not really any RIGHT way to view him aside from the not-completely-wrong ones--there's a lot of room there to work with, I think you'll agree).
I'd say that Abelas and Solas are about on par, maturity-wise, but then I believe I look at it differently than you do. You say you see someone who's a user (and using someone is downright abusive, in my opinion), but I see Solas coming to realize that the Inquisitor is his equal as she begins to actually wield the power that she came by--even if Solas did help with that. He uses the Inquisition as a whole, but I don't feel he ever tried to take advantage of their relationship by playing on the Inquisitor's romantic feelings for him. If he had, that would be less "immature," and more "completely unforgivable." Some people see it that way, and they are welcome to--and I would totally understand why they'd hate or just not like Solas. I don't see it that way though, so hopefully you get that, while I despise what Solas is planning to do, I can see value in the relationship between the Inquisitor and Solas. I just wouldn't want to be in anything like that sort of mess, myself.
If there were to be a romance with Abelas, I think he'd be rather depressive, and I don't say that to bash the character or make light of depression. He did rename himself Sorrow (Abelas), after all.
The ultimate happy ending for Abelas (in my opinion) would be deciding not to enter uthenera, but instead to live (even if he must live as a shemlen, assuming certain things do not come to pass)--a friend or a lover could convince him not to give up. His conflict would probably have something to do with remaining bound to Mythal, and Mythal is likely to start showing her grey morality side soon (I expect her to oppose the protagonist of DA4, even if she also opposes Solas. She's up to things, I don't doubt it.). So, in love with protagonist, but he may have to oppose the protagonist. If Mythal doesn't make him do it, he might have to do it of his own free will by joining Solas in order to be freed of Mythal. A true happy ending, relationship-wise, might not be possible in light of that. Trust issues would likely arise if he opposed you at some point while bound to Mythal--even if he were later freed. He was loyal to her, as far as we know (though his loyalty may also have faded, and perhaps he was simply guarding the well in case the world was restored, or to keep others safe from its power and the cost thereof--we don't know).
I guess, long statement short, I'm just saying: You can like them both. I like them both. There's nothing wrong with that. And I also criticize characters I like (yes, Solas included--especially Solas--I was very hard on him after beating Trespasser, but have since come to terms with it). I've seen jabs made about not just the characters of both threads, but the actual fans-in-general, and it's put me into an uncomfortable spot because I frequent both threads and see it on both sides.
Sometimes I'm kind of afraid to post in this thread--which is the main reason I haven't posted too much the last few days. I've been pounced on as a hater in this thread a couple of times simply for stating my personal opinion or adding neutral input into a discussion, without having any hostile intentions.
I am the kind of fan who likes to think up theories and discuss lore. I often try to be rational (when I'm not trying for funny or feels), and sometimes, yes, that means disagreeing with people or speaking in a neutral rather than passionate tone about the topic. If we all 100% agreed, it'd be kind of dull, though, wouldn't it? Even in the Solas thread (where I post quite a lot), I mostly talk about motivations and lore and how it pertains to the characterization. I am not here to tear down anyone's headcanon (even if I disagree with your opinion it doesn't mean your opinion is invalid) or crush anyone's dreams (I'm hoping Abelas is in the next game, too--he'd be interesting, no doubt). I like discussing characters. I'd like to see Abelas actually be fleshed out more in a future game/book.
I think Sable came here to discuss, too. Sometimes people can bring interesting things to the conversation even when they disagree with you, or because they disagree with you. Not everyone is disagreeing because they are a hater or want to cause trouble or get into an argument. Sometimes people just... disagree.
Sorry if I'm stirring the pot or anything. Just my two cents, trying to stay neutral.
I'm looking forward to a Mage romance that doesn't end in "run away!" or ya'know "I made something go boom!" I'm also looking forward to a Dude Elf romance option that doesn't leave at the end or the middle. With zero commitment issues...*sigh* A girl can dream. Abelas seems like the type to stick around. He has issues most certainly but, he isn't lacking in devotion. Ages guarding a temple and he didn't leave once...not even to go get snacks. Sign me up! lol 
Abelas probably wouldn't have commitment issues, no. He stayed with the Well for thousands of years despite thinking Mythal was never coming back. We don't know how much of that was because Mythal told him to and how much was simply because he felt the Well needed to be guarded (for any number of possible reasons).
I too would like to see a mage who turns out to be a stable, healthy romantic interest in a BioWare game.
However, as I noted above, that might not really be a role Abelas can fulfill, at least not without a lot of hardship beforehand. He remains bound to Mythal. If not Abelas, then perhaps some other Sentinel could fulfill the role? Yes, I know it's not the same, but better than nothing, right?