WOW. I love the game design. Those graphics are really beautiful. I don't know if you use the free edition or if you have purchased a license, but your project seems big. I hope you will be able to do what you want.
I'm not an expert in apocalyptic games and I think you have already thought about it. If there are survivors, I will suggest to add different class of people such as doctor, strong people, etc. Therefore they can interact with each other.
Do you plan do add monsters in the game or just survivors? I will stay tuned because I'm very interested in your game. Good luck on your game.