Isn't it like this already? Or is this just in GG mod? I was under the impression (even in ZM) if a map was played, when you nominate, you cannot nominate that map since it has been recently played.
I'd also like to note, I know LOTR maps are always on map votes, and it does seem dull to play, but you all have to admit LOTR maps bring in a SHIT load of people.