Great idea actually, especially co-op mode online or a battle mode online.
I have a suggestion for the game as well. Why not a Boxhead were you send out zombies at your opponent. It would be great. There could be many levels of zombies, and you could be able to give them guns and weapons.
I think that Boxhead online would be a brilliant idea, i remember how much fun it was to play just against my brother but playing against people of varying abilities would be a great test of skill. (Because let's face it, you'll always work out your siblings tactics, weaknesses and strengths after a while.)
This is a fun idea but if you make it go online there are bound to be hackers who will corrupt this game with their ways... Then make it hard to get a decent cheat-less games.! Am i right? The worldwide version could be pretty Laggy because of the amount and the range between people.. BUT This is a great idea! You should send it through to the producers of BOXHEAD gamings! GOOD LUCK WITH THAT!!