How about if you had to make a World XI which is balanced by continental federation roughly proportionately to World Cup berth?
So roughly, 4 Europeans, 2 South Americans, 2 Asians, 2 Africans, and 1 North American. Just to make it more interesting, you're not allowed to use 2 players from the same country.
This was the best I could come up with
Howard(CONCAF)
Lahm(UEFA) Thiago Silva(CONEMBOL) Vidic(UEFA) Nagatomo(AFC)
Yaya Toure (CAF) Xavi(UEFA) JS Park(AFC)
Ronaldo(UEFA) Ba(CAF) Messi(CONEMBOL)