There should definitely be some sort of payoff for the fix, for sure. I don't expect the devs to sell a perfect happy ending for her because that will just create an outrage with the other Origin's fans. However, just like I chose to save Sharts parents at the cost of her never getting rid of that pain, and picking Astarion's well-being over the fact that he won't be able to stand in the sun again, I would definitely choose a less powerful Karlach or even forcefully retired Karlach (who wanted to go on adventures in Faerûn after the events of BG3, mind), over a dead Karlach or Karlach back in hell.
Endings and Origins discussion below:
The only one that really gets out without much of a fallout is Gale when he brings the crown to Mystra. Though I don't know for myself just yet how Mystra taking him back under her wing affects his relationship with Tav (given Mystra's grooming tendencies and Gale's deep connection to her). Lae'zel staying with Tav feels good for the romance part, but comes at the cost of her greatest wish - to become Kith'rak and ride a red dragon and wield a silver sword, now as the liberator of her people and strongest Githyanki alive. So that's a 50/50 choice, much like Shadowheart's parents and pain vs no parents and no pain but deep regrets instead. Astarion is much more evil vs good coded, but what's interesting is that his story never takes him to free himself from vampirism. If that were the case, I feel like curing him and leaving Karlach to die would've made an even greater earthquake re: what's fixable or not with a fantasy realm at hand. Wyll has a solid set of choices Imo, the only part lacking is that his story is so light in content especially in Act 2, which on one hand isn't weird given Shart and the shadow curse take the scene, but I still feel like his story could've used some more meat on those bones.
