Classic turn-based ?

[Ygorl]

You could partially take care of income, gems, etc. by lowering site frequency and world richness. Disease and age would become more important (unless you modded the game to raise lifespans, e.g.), scaling with the number of players. I think it wouldn't be too hard to tweak the game engine itself (speaking for Illwinter here) to make this kind of hack a little smoother... I like simultaneous turns so much better than sequential, though, that I don't know why they would. That was one of my favorite aspects of Diplomacy, but it's always so hard to get a group together to play...