I have had her in my party again for a bit recently and it has made me painfully aware how much the game tries to shove her into the spotlight. She is the only character everyone expresses concern for, she gets a lot of little moments to make you feel for her, she gets dramatic or likability moments at the expense of other characters and she's even got the specially modified romance scenes. If there is any character in this game who does not need any more attention, it's Karlach. If that whole journey to acceptance turns into content that allows poor Wyll to properly shine, I am all for it though. The boy needs some love and some stuff to do.
Besides, the want to live is part of every character's heap of troubles in this game, even excluding the tadpoles for some. But at some point the basic question of survival changes into an exploration of what a liveable life looks like usually by putting previously held believes or wishes to the test. Following your story, Karlach's conflict is just a second "Find a cure" quest, nothing about her perception of the world gets drastically challenged in any way. The only thing she might learn is, that Hell does not necessarily mean to be alone - which could tie in nicely into "after all what is Hell without Hope" if you want to give it a super nice evil twist.
That's an interesting take considering those small moments are pretty much all she has. She doesn't have a fleshed-out storyline, entire zones, whole chapters, and large subplots dedicated to her like the others do. If you take that away from her, what does she have left?
Following the arc that I outlined, finding the cure takes a whole different meaning. Survival and living are two different concepts. Now Karlach doesn't want to survive, she wants to live a fulfilling life. Because she didn't envision it before, she was ready to die, surviving only as far as it allowed her to accomplish her final goals -- to die free, and die a hero. It was the same for everyone else. They each had their own goals that they wished to survive long enough to accomplish. None of them, however, needed to be convinced that their life was worth living. Only Karlach.
Putting that aside, what changes about her perception of the world is that she now understands that she can't simply run away from hell and make it all better. She has to face her problems head-on. If it wasn't for us, she would've kept running until she died on the surface as she originally planned.
