That's both interesting and ambitious. Indeed, IWD-in-BG2 engine looks like a success, in my opinion, and a huge bg-iwd space might be a head-turning project, too.
I'm very sorry, but I couldn't find your project on SHS. Is it complete, is it in progress, is there a beta, a suggestions thread? Sorry, I couldn't find a separate forum so I was a little lost.
I think it has merit, but first and foremost I would consider this: if you go to IWD with BG characters, it means that you'll be playing the plot of IWD (as a HUGE subplot) with BG characters. That means that you'll need extra interjections and scenery dialogue (with optional romantic branches) for Anomen, Jaheira, maybe Kivan and Xan, etc. That WOULD be very cool, and that's what I would start with.
Because otherwise, sure, one may write banters with, say, Nella and Jan Jansen, but that would make little sense if Jan is silent throughout IWD content. (If you take a look, IWD NPC chars banter and talk in every area and every major conversation, and I don't think it's too much - it makes the game interesting).
So, I would propose IWD scenery conversations and interjections for BG companions as a good first step. (maybe not EVERYONE, Faldorn and Quayle and all, but at least Minsc and Imoen and Jaheira and other fan favorites). Then, when they're talkative - more crossmod.
I'd be interested (though I'm busy with some other stuff in the coming weeks), but I think I'd have to know more about your project, and if I might suggest it (sorry if it's not my business, just a thought): you may need more marketing - i.e. recruit people at G3 and PPG, advertise your mod, get a forum board at G3 or SHS or PPG if you haven't already and so on.
EDIT: Storywise I would just offer to forget the timeline. I.e. don't think about the year at all, forget that topic, say the events happened roughly in the same few years, that's it.