Well my Idea was to have a "Galactic Realpolitik" (excuse me if I misused Galactic, it honestly was the first thing to pop into my head.) where every player was a delegate for their country at the Council of Nations. The objective would be to colonize other planets and eventually dominate the Council of Nations and be made Emperor of Man. However, the problem with that is that 1 CiV has no modern earth map, and 2 that I am unsure what exactly the council would vote on. For the first I did find a CivIV map that could be converted, than modified to fit CiV. However it doesn't really matter if the map "works" for CiV because actions on the earth map would be severely limited. For the second I thought that maybe I could create International Issues that needed solving. The Council of Nations would have a Chairman and 3 Councilors. The Chairman's vote counts as 2. One of the councilor positions is appointed by the Chairman, one by the opposing party, and one is elected to the position. Only the Chairman or the Councilors can propose legislation/resolutions. If 3/4 Councilors and/or the Chairman agree, they can veto a resolution or a law. System subject to change.
My second Idea (which I'm coming up with now on the spot) is that we could play the Iroquois on a Giant Earth Map, each player being a delegate from one of the 4 tribes (Mohawk, Onondaga, Oneida, Seneca). New cities cannot be founded. The tribal council would direct research, workers, Social Policies, and even production (though tribes can choose to follow the production plan or not). While Chiefs would direct faith purchases (the tribe earning the most faith gets to decide), unit orders (military not domestic), and have the final word on production in their city. Chiefs cannot be delegates to the council. The council is made up of a Head Chief (acts as president, production, gold purchases and national agenda), a Wise Man (research and social policies), and a Master of the Hunt (directs workers, and in times of war coordinates the units of the different tribes. All positions are elected. The point of this game would be to unite all the tribes of the Iroquois into one, and defeat the other new world tribes. Technology in this game will be limited to the Classical Era.