Expedition: general discussions.

I once had an idea to host a forum where players would capture a city divided into sectors, with each player representing their own faction.

If that's the case, you could expand it to an entire state; why limit it? However, the idea is quite interesting: alliances, nuclear bombings, uprisings of the civilian population, and encouraging revolutions in other countries/parts of the city – there's something to it, if implemented intelligently, of course...