Nothing mode to add. Just hoping, that future patches will add deleted content to the game and fix my and Karlachs hearts.
I finished the game two days ago with good character and romance with Karlach.
I helped Wyll to be the blade of avernus and collaborate with the emperor. After final scene on the pier I hade tears in my eyes the whole evening. Only Wyll could took Karlach to avernus, so no options to go with me instead is obviously wrong and make no sence at all. I expected the whole game, that I will be able to fix the engine and visited the smithy after each main quest or Karlachs quest completion and nothing. After finishing Karlachs questline I expected another one and nothing. Then I expected some way to visit avernus, kill Zariel and fix things somehow there and nothing again. I saved everybody in the foundry, had infernal ores and nothing. So literally I'm not able to start the game again until there will be better option how to save Karlach.
Fortunately datamined files gives me hope, that this will be patched or in definitive edition. Thanks Larian for the best Rpg of the decade and for me one on my top 3 all times (BG2 and Divine Divinity), but Karlachs fate just killing me.