I could see one giant island... if we didn't have all these cool Biremes floating around... and soldiers who enjoyed water skiing between conquests.
I think if we made a smaller world, we'd need to limit alliances... say an alliance can't have more than 20 players or 20% of the total points of the world...
And like the Highlander... in the end, there can be only one!
or two if they're Siamese Twins... cuz that seems gross that one would have to cut the head off the other and then drag a headless corpse around for the rest of his life.