If they would help at the end, why not? If we got an ending when she doesn't have to go back to hell but needs help with finding soul coins, and you would just go into the world to search for them, why not? Also I listed many arguments why the potential soul coin ending is not good either. And what's sad, it still would make more sense than the current one
Infernal engines is fueled by the souls of mortals. Like, lets take BitterSchizo, we squeeze out his soul and transform him into a soul coin... Now we put this soul coin into Karlach like a slot machine, and she work for another day... So lorewise, if you convince Karlach to have her return to Avernus, her life would be dependant on keep be fueled by souls of mortals. You can have her turn into a squid and crave brains in stead. ;p
