I can't think of any interesting theories. What have you guys brainstormed?

Probably something similar to Vault 112 given their numbers are close to each other.

I'm clueless but very curious - Cyrogenic tanks seems to be the common speculation

I'm thinking a Control Vault. Any experimental vault has an alarmingly high likelihood of having gone horribly awry and leaving a dead vault behind.

Yeah cryogenic tanks, and androids, is what some people think. I hope it's true. It's refreshing to be able to really be an android and not just the same human being all over again. The only thing better would be vampires, heh. Well okay I prefer cyborgs to androids. Still, better than a human.

But I doubt the android part is true.

Another police-state vault like 101 would be interesting

"All hail the Overseer - We are born in the vault and we die in the vault"

That's my theory.

Preservation. Vault 112 was all about preserving the mind. I don't see why Vault 111 wouldn't have an experiment about preserving the body.

Personally, I think Vault 111's experiment is about testing the long-term effects of cryostasis, or even experimenting with how viable it is. We've seen several instances of cryostasis in the Fallout franchise before, but it has always been depicted as an unsure thing, and quite dangerous. Vault 111 could be an experiment using multiple kinds and conditions of cryostasis to see what works best. Certain vault residents are periodically thawed out to test if they DO wake up, and the results sent by computer to Vault 0. Our Vault Dweller could be one of the lucky ones who got a successful experimental cryochamber, and is one of the last to be thawed out, and one of the few that is actually a success. Most of the other residents of Vault 111 are probably freezer burned corpses dead in their pods.

EDIT: If Vault-Tec DID assume large scale success with cryostasis, Vault 111 would make an excellent backup control vault. No genetic degradation, and no in-breeding, and they could keep the residents on ice as long as they needed to maintain a control group.