Ok so my idea is simple and people like it.
There was a virul outbreak, there is a lack of anything.
In an abandoned city you are in a group trying to survive (you can only get in the world when there is more then X amount of the group online)
You find an abadoned building and try to make it safe, creepers can spawn during the day and can BLOW your safe zone up.
There are a lack of mobs and they don't spawn as often.