The people who can afford to pay for this can also afford to avoid the worst effects of climate change, probably much cheaper while throwing the rest of us under a bus.
I want my street, my house, and general geography to matter in the game. Where is the hardware store? Army bases? Water?
The game starts with a limited infection, making police response to your murdering an infected neighbor problematic. The simulation models how agents would respond.
You win by killing all the zombies, whether that's year 1 or 10. If needed, that's 7 billion.
The exhaust could be a good city simulator, zombies off, which you sell to local governments.