I just thought of something.
You know how wastelanders are ambivalent about vault dwellers? At most you get snide remarks about your common sense when you talk to people, especially early on.
What if everyone was outright hostile to them? What if people were trying to break into vaults to live in them in a coordinated and real effort? What if 'vault hunting' was a prestigious thing?
After all, these vaulters live in high-tech, cushy lives while everyone outside gets fucked and dies horribly. And often vaults don't want to share, are locked up for an arbitrary number of years, or emerge and try to be like Vault City.
And to keep it varied, it should depend on many factors and be different for settlements/factions. Some might try to kill a vaulter outright for the pip-boy (making the 2000 more wanted than the 3000 since you can hide it better). Others might use hostile diplomacy to force vaults to share their tech and expertise, to 'add onto the common good'. Others might try to take over vaults outright, especially if they think the vault is 'underpopulated anyway'. And of course, some vaults fought back and might be trying to control/enslave the wasteland.
That'll be a nice thing to add to a game, especially maybe one that is set only a few years after the war like 76 is.