It sounds like the general consensus is starting the player-nations off humbly and building them up, with the GM actively arbitrating situations the players can't settle, or otherwise implementing some sort of point-system. 

I'm totally in favor of a humble start, but neutral on the matter of arbitration. I'm perfectly willing to make rulings as needed if players can't settle things themselves, but if anyone has previously experienced a nation roleplay with a decent point-system for arbitration, I'd like to hear a bit more about that. Ultimately, it'll come down to whether you guys want a system or structure to come to agreement with each other, or if you want the GM to make a decision when things can't be settled.