I respectfully disagree. Astarion is finally happy with who he is, finally accepted that he's enough.
He has made no indication he has a desire to return to human life. He wants to be free and also wants to walk in the sun.
You fixed the first issue.
The questline for a nonascended Astarion is that he discovers he's enough and worthwhile exactly as he is -even as a vampire spawn.
He doesn't need a cure. He needs a solution to walk in the sun. They aren't the same thing.
I agree with this. I don't think he needs a solution to walking in the sun - he should exit the scene before the sun even rises in the epilogue, so he doesn't get burned at all. But I think his first stated goal as a spawn is finding a solution to being out in the sun, even a temporary one, and then working with Jaheria - and the MC if they wish - to find a cure for vampirism. But not explicitly for himself, instead for all the people he helped enslave and turned into vampire spawns.
