100% agree with this.
I would also love an option for having a fixed number of zombies in the world and wiping them all out would be a way to "win" a map, but I don't see this happening. It could be simulated just by having the game go through and total up the number of zombies that will spawn...
I used my sunny disposition to grow shrubbery on my head. Then old age turned it into a weeping willow. Now it's more like getting a bowl haircut with one of these: