Well, Swen gave as close to a definitive "no" today as I think he ever will. He basically said it was too complicated to involve multiple characters in a dialogue, that they tried it and that it didn't work.
As it is, I could maybe see a script mod (assuming those will be possible) that just grants party skills to the face during dialogue, who would then appear like a Mary Sue who knows and can do everything. That would mechanically solve the problem of party members not contributing, but it wouldn't be particularly satisfying. I'm not sure I can realistically envision anything bigger than that, though.
