Quite interesting, but...
Nah, again - gameplay mechanics subverted for the purpose of cutscene. We need either third agent or C&C.
So wait... how come acid in the face is subverting gameplay mechanics, but a squad of elves with bows isn't?
Acid to the face - you usually dodge all bombs, flasks and even fists during gameplay. Taking away control from the player so that Geralt is hit with the acid bottle == subverting gameplay (I grant you - it's still better than what we have now).
Remember that they fallen in a hole. Nobody knew where they went. Only after the fight was over.
Auckes finding you takes place outside of the gameplay within the frame of the story. Auckes could outsmart Iorveth by essentially doing what Iorveth was planning to - watching the whole battle from the shadows, following Letho's and Geralt's fall and then pushing through the where they were (which takes time, waiting for Iorveth and Roche to bleed out).
This would be merely a plot development and no gameplay would be denied in this way. This is entirely fair and accounts for player's accomplishment without killing off the antagonist (in fact this would allow a character development for his lackey).
I would see the acid throw in the cutscene more like this - Letho gets beaten, sword out of his hands and lying on his side. Geralt wants answers - he's pissed and during his talking Letho does a dirty trick, acid + aard for the bottle to break and spray. Geralt is fast and saves only half of his face. It still burns like a mother fucker, but Letho can escape. Dirty move - the characters later remark about it and want him more dead (even the player for that underhanded thing).
Auckes watching the fight gives us more questions than answers. Why Roche's people didn't see them? Are there two good spots to see the fight? If Roche/Iorweth people didn't see during the fight the collapse, then how Auckes? If the Triss+Geralt moment doesn't occur, then how they know about the secret passage?
I agree, but it would need more than cosmetic changes.