So, my idea is this:
The players go around a random tile board( sort of like Cataan) and explore the land around them. They are going around to find supplies for their burnt out city to rebuild. The way this will work is that the city has a board on the side by it self where it shows what has been built so far. As far as the survival part, the players at the end of each round and during the encounter phase if they encounter an enemy have to fight monsters, zombies, aliens, raiders, and various other things ranging from a swarm of nanobots to a time traveling wizard. The players will get points for beating monsters and they will get points for being the one to bring back resources for a building. For example, player 1 brings back enough resources to build the hospital. He gets 3VP and the other players now can get a free med kit when ever they come back to the city.
this is the basic idea so far, I'm still trying to flesh out the mechanics without making it too complicated.
i'm thinking that they awoke from stasis pods or something to get around that detail. Like, a lot of time has passed and the landscape has changed.