Vault 59

Puggsly - Kemmerer would be a fantastic place for a Vault, one that follows the plot of Time Out of Joint and the Truman Show. Pre-War, FEV testing created some of the first Psykers known to man. Unfortunately, the new abilities given drove most mad. In an attempt to save their new super soldiers, the U.S. government stationed most of the Psykers and their families in the Northern Commonwealth. This isolated setting helped them to prevent the intrusive thoughts of others from destroying their minds. A Vault was constructed here, as the government (Enclave) planned to use the soldiers for their own purposes following a nuclear event. Because the FEV exposure made them sterile, all inhabitants were preserved in cyrostasis, with an accompanying virtual reality simulation ala Tranquility Lane. Unlike Tranquility Lane, there was no Braun figure, meaning the experiment carried out normally, until one of the men, Lloyd Burbank, slipped and fell off of his roof, snaping his neck. When the others went to bury him, Lloyd suddenly appeared alongside them, and alongside his own body. They then realized that they were all housed in a simulation of their prior home. The people inside has desperately searched for a way out of the simulation for years, as the Vault continues to run at peak efficiency. Some have sunk into even worse hysterics, continually killing themselves and being "resurrected." As the inhabitants are Psykers, they would communicate with the Player as soon as they use their Pip-Boy to open the Vault. The Player could go inside and free the people, go inside and kill the people, shut down the Vault for scrap, so on.

The Liners being ontop of the Vault could be a plot point. Maybe they're the ones trying the bust in for valuable salvage, but can't get past the door without a working Pip-Boy. When the Player shows up, they can offer their services in exchange for a reward, becoming an ally, or something like that. Still not entirely sure.

Atlas - I like the idea of tying the vault with the Iron Liners.

In fact, i am just thinking that perhaps one of the strongest Psykers in the vault is somehow capable to mess with the mind of the Iron Liner's leader. Causing perhaps some slow descent into madness for the Iron Liner leader? It could be like a witcher 3 quest, where you have to investigate what causes the madness and discover about the vault that way.

Puggsly - Haha, that would be fantastic. He's trying to be like some sort of god figure to the Liners, subtly convincing them to enter the Vault and free them all, but he just "interprets" the messages as what he wants i.e. "get more caps, women, and turf," putting the Vault on the backburner.