I agree with tlasjr a axis and allies based modern combat game would be awsome, have all the worlds major powers fighting each other for todays statigic locations. I read alot of feorgin affairs/econamist/stratagypage/ which often talk about the global military situation and i would love for a game to represent that.
the main things in the way of a game like are.
1. In todays world important dicisions are made by banks/multinational corporations/popular opion instead of fascist/socialist states that command the entire soal of the nation they rule, this makes long protratracted war unlikly
2. You would need a whole new map with new peices which would be very expensive
3. You need to makes space a battlefeild which is hard to represent on a 2 d board of jeust earth
4. FInally Allieances are not set it could be US/EU/China/Japan vs India/Russia or just as easily US/EU/India vs. Russia/China/Iran
so alliancs would have to be maluable or their would have to be many different scenarios. I would also make the turns represent shorter amounts of time even as short as two weeks.
plus what do you do to simulate gurillia warfare which is so prevelent. If the game has two week truns through then it is less of an issue since gurilia warfare would be less of an issue