I'm sure this was already mentioned, but I just joined the forum so I don't have time to seep through all 122 pages of it and just wanted to publish my thoughts, lol.
Anyway, it's obvious that Karlach is the character that had the most content cut from final release, as she was the last addition to the companion roster according to what I've heard/read. Supposedly there was to be the entire area of the Upper City to explore that Karlach's quest would go into that would probably was going to let us fix her engine permanently, but alledgedly that was all cut almost last-minute before launch. I can understand if it's too complex to add and finish it at this point, but at the very least Larian should repurpose that cut Karlach content and change her quest so it lets us fix her engine with what there is already in Act 3.
I feel the best way to do this, and was already HEAVILY implied was going to be the solution but was ultimately cut, would be to use the Enriched Infernal Steel that some Steel Watch units drop and the Gondians doing their super-engineering magic to fix/alter/rebuild the engine with those materials as a reward for saving them, giving even more reason to save them from the Foundry as well as more reason for destroying the foundry/eliminating the Steel Watch. Would be a cool ironic twist of fate too: a creation of Gortash being used to save the life of the one he sold into servitude to an archdevil.
If Larian did this plus expanded on the epilogue to show more of what happened to companions and primary NPCs as well as the lands we went through in Faerun (especially around Moonrise Tower regarding the shadow curse and all that) after some time has passed following the final battle, then I'd probably rank BG3 as my game of the decade.
The thing is that the rumours about "good ending" for Karlach or avernus as explorable area being cut were fake. Yeah, some content was cut from her, but it might as well be Gondians and Steel Watch explaining why they can't fix her (which is why it wasn't moved, but Astarion's content was - while it would expand upon her arc, it wouldn't change it and Larian was already short on time, which is also why she's the only one with the mindflayer option). I'm not saying her story won't be changed, but the fix very likely wasn't planned, at least not from the begining
