Had a similar idea myself, something sort of like Fringe with two separate games where players would be assigned a 'home' thread and each would have the standard split of natives/outsiders and getting voted out sent you to the opposing thread. Main issues being coming up with a sensible win condition and some way to permanently remove players (maybe only able to pass through a portal once, teams have to claim both sides). Would be a logistical nightmare. Would need to have a separate forum and give users per thread permissions with a new thread per day phase.
So I've heard of a were wolf variant with two villages. Both start off with an equal number of everything. Rather than lynching, you vote to send players to the other town. The point is to end up with a village that is entirely town.