Theme: Control Freak Experiment
The Experiment: The Vault itself is surprisingly normal. Except for the lowest level where there are weapon stockpiles, Deathclaw eggs, etc. And on the ceiling are "sprinklers" that can spray very noxious toxins in a very controlled area. The lowest level is blocked off by a powerful blast door that requires a button that only exists in the Overseer's office. The same office is also blocked by an even more powerful blast door which requires a password to unlock which in turn, is locked inside a somewhat fragile door.
The point of this experiment is that nobody knows what's behind that fragile door and instead, are taught from childhood that the door houses a vicious mutated creature. The people of the Vault can live in peace with no idea how much power is inside that door since there is no weapons or armory other than the lowest level which is blocked off. Or some brave soul can smash through the door with a hammer and discover the Overseer's Office password
The office controls EVERYTHING. Anybody with access to the office can turn on the sprinklers in ANY section, open the lowest level, and even blow up the Vault.
The point is to observe whether or not somebody with absolute power will harness it for good or evil. Also as a side note, whether anybody will even think of going into the room that holds the password or not.
Predictions: Within 10 years, the door will be smashed open. One man takes control of everything. Here's where it converges
It could turn into a utopia society that is controlled by one autocrat or it fails in a mere month with everybody but the overseer alive.