Yeah, something like a director's cut, or something that rebuilt the last part of BG II or ToB so they didn't feel so linear...stuff like adding back in cut romances (think there was at least three), bringing over more of the BG I characters or fleshing out the disparity in content between the class strongholds. I'd have loved that.
What gets me about the restriction I have heard about what they were and weren't allowed to touch in the EEs is what I have read about in SoD... They were allowed to bring back a whole slew of original voice actors to add new content to old characters, including in one case, a new romance! So how much leeway did they have? Was 'you can bring back old characters and write new romances for them, but it has to be in a DLC and can't carry over to BGII' really a stipulation? AFAIK even if you have her as a companion/romance in SoD Safana still dies in BG II. The fact that SoD inserts a completely new storyline in between BG I&II seems like it could have been possible to add new story content to the games, or was everything new storywise on a 'strictly self-contained' stipulation?