That sounds like a extremely short and boring DLC, sounds more like a individual quest inside of a DLC.
I know. I think it's a great idea for a quest (of course I do, or I wouldn't suggest it
), but I admit I have trouble playing it out to a full-length DLC. Unless you have to persuade
every single person out of a full 1000 people to leave, muahahaha. *Ahem* I don't know, perhaps if they implemented a vault in-game to the scale that it should be. You see this sort of thing in games all time (Oblivion being a perfect example). Oblivion gives you Imperial City which is supposed to be highly-populated, but in-game it's pretty sparse. The real reason is that designers don't want to put in 100's of NPCs that don't really
do anything (since that costs time and money), so the NPC's that
are in the game are given the rationale (even if it isn't voiced by anyone as official) of being representative of the whole population.
The picture in my mind that I had for the idea would have been a huge vault - much larger than Vault 101, for instance, so you'd have a lot of interaction to deal with.