Survey SAYS: Without Demetrias 100!!!!
Ding Ding Ding!
Anyways, since it seems that Fuschia has the spot, I would reccomend either the African Union or Russia. If you want further musings on Russia's future, don't hesistate to ask/pm me. I don't want to impose upon your play though, I'm only offering ideas on both.
A resurgent Russia would definitely provide your Europe/America counterweight though, Fusch. They're the clear cut forth major power in the world's realignment, and any wild card should be the fifth. Russia borders Central Asia, China and Europe, giving it direct connection and influence over the areas that will be undergoing some of the most change. Additionally, it has large interests in Africa.
The African Union provides an interesting federalist combination thats very realistic. Unifications(which looks likely) could be wildly successful if a stable government is in power and some sort of strong Pan-African identity takes hold in place of tribalism, which you could easily make happen in the large scope of this NES. The Afro could become very strong, and if Africa can really regain control of and exploit its own resources, then it can quickly rise to a top tier power.
Just my thoughts on the issue. I'm really dieing for a spot, or some hand in the history. If Chand can find in his benevolent soul a spot for me or my comments, I would be much oblidged, and not n00bish.