I think its more to do with the obvious potential that Karlachs story has just kind of ...sitting there. yes another fetch quest could Solve the issue of her ending and if Larian goes that route id still be grateful for it. but I think most of us want something akin to shadowhearts temple of shar, or astarians cazador mansion or even Lazels Creche. a section of content that fleshs out her story and gives some good closure and player choices to decide her fate. like even just a raid into avernus using that shopkeep in act3 like the house of hope to get something to fix her heart? or somehow even replace her engine with her REAL heart. that would be poetic and beautifully fullfilling IMO.
