Zombies!!! XXXX

 

You'd have to go big on the 40th expansion to Zombies!!! which is why I'd include a helicopter mini into this set along with player boards to keep track of all your items and a reminder of the gameplay. I'd also add more city cards and some city worker zombies for the base game. 

I'd also make a special mayor zombie figure who's harder to kill than the others and is your goal in the game. Plus, I'd add a bus route which is constantly on the move during the game and allows to you to move around more quickly getting off whenever you want to. But you would need to collect coins in order to pay to ride on it. (it's automated let's say) No coin? You get dropped off at the next location. 

It'd be a unique idea for the game I believe.