Though it’s a rougelike game, we can still create some interesting random polts.
For example:
Gang fightings as the story of “the governor” in Season 3.
War may raise because of another group of human beings’ invasion.
or
Invasions by player’s group, and the human defenders will protect their stronghold - a mansion, a building, a castle, or a part with sufficent resourse, etc.
Some NPC can be created such as soilders, survivors, doctors, explorers. Each has different characteristics, properties and purposes.
The ideas all above will definitely increase the fun of the great zombie survival game.