I would like to keep the mod nations to a minimum myself. I played in some all mod games recently, and I did not feel that they were terribly well balanced for large scale multiplayer.
So be it. We'll get Ramz get a mod nation. We'll have the game limited to three mod nations, and stop accepting any new players. Three mod nations out of 21 shouldn't unbalance the overall gameplay too much.
If they are too strong, we should be able to manage a strategic alliance and offer the mod creators some feedback.