Game World Options: Mobs Advance Settings

Before starting up a new world, being able to customize the Mob settings. An advanced settings category that allows you to activate which mobs will be spawned. Also being able to deactivate "sun (and, or) torches prevents mobs from spawning". These would give a great effect to world. With these two settings you can come up with a plethora of "themes" for a world. Not only being able to choose what mobs spawn, but also the frequency of spawn. 

Having the ability to create a world with a "Zombie Apocalypse" theme and trying to survive in it would be phenomenal.