@devonapple: I quite like your suggestion, but I don't think it'd work for social conflicts where the participants cannot be divided into teams. How would you adapt that approach to model 10 diplomats from different countries sitting around a table at a peace conference?
I think you'd have to go with the Diaspora model using my suggestion. The alternative is to define and codify numerous individual Conflicts, all of which are competing with another.
But let's back up: what is the reason for that scene in the first place? Who are the player characters and what are their goals? I suspect that such a scene could be distilled to get down to an essential, meaningful conflict or two - the rest of it is just noise, background chatter, etc.
It's like simulating mass warfare in a tactical game usually used for a small party of adventurers: what do we really need to know for that game to be fun for everyone? D&D started out as a mass-combat tactical game and then zeroed in on the individual role-playing. And that's where most of us are, now, in the games we like to play.
So going back to the diplomatic party, my impression is that the list of desirable outcomes for our heroes is actually not that long:
1) pick and back a particular diplomat's agenda
2) uncover information about a diplomat's agenda
3) influence the outcome of the negotiation
4) gain allies
One could run the negotiation as a complex, sandbox-style set of conflicts as a way to avoid railroading. Or we could, more simply, address the goals the players have determined and let the rest of the negotiations be flavor, cutscene, predetermined unless the players exert some influence. Much like a battle: at the beginning of a mass combat, one of the sides has an advantage of some sort, and if all things are equal, they should win: if the players aren't there to impact the outcome, let that side win. The stakes for the players will be to influence the outcome and turn the tide, so we determine what they generally need to do to turn that tide. Maybe the players' chosen side is doomed to lose, and the players are there to mitigate the disaster, or to take advantage of the fog of war (or their sides' noble sacrifice) to accomplish another goal with less resistance.
