As opposed to the path of Ascension, there could be a path of Healing (as I see it). If Astarion could be completely healed of his vampirism and gradually regain the self he was before he was captured by Kasador, overcoming his traumas and gradually learning to trust the world again (to a greater or lesser degree) with Tav's help. If he was independent while doing so, he wouldn't try to "fix himself" but would simply start smiling more and more often, joking, having fun for real, rather than using a smile as a mask. He could start treating those around him better because he feels like it now (and when he feels like it, not by adjusting to Tav). And, most importantly, would have accepted and loved himself. This would be a great option for Astarion's "good" path, maybe too "good and sweet" for a "harsh and dramatic" game, I don't know, but then you could "walk the good path" the whole game with pleasure, and stay in a wonderful and "warm" emotional feeling from it.
This is the good path in the game, especially the non-romanced, non-ascended path.
The only thing, which doesn't happen is curing his vampirism, but it's mentioned in the epilogue that he accepts it as a part of himself.
