It would be an RPG game along the likes of LOTR or WOTB, so likely single faction. It is possible to play multiple factions in such a game, but we'd need a good number of starting players for that to work.

Broken Crescent is my favorite choice for a mod, although if the new version comes out soon we'd have to discuss whether to use it (since it requires Kingdoms, which could make it harder for some). I'd also note some objected to a mod that wasn't based in Europe, and the mod chosen would likely be voted on.