In other games, an issue that tends to arise is that too many micro alliances show up. I can see this in a way here with the plethora of one-nation alliances beginning to pop up.
I suggest that a (small) in-game fee be put in place to create an alliance. Not a fee large enough to break the bank, but just large enough to make someone really think that if they would like to invest in their own alliance.
I think $500,000.00 would be enough to suffice.