I really like the vault idea. We could have SPACE GOLD! Make entrance into the vault require all the head ID's (Maybe pins too? I dunno, I don't like requiring pins because it makes identity theft that much less effective.) Alternative ways should be extremely difficult, something like sneaking in through the mining dump, (Gotta add more space gold all the time, right?) controlled explosions, etc. Make sure the vault is in a highly visible location, with IR detectors ready to scream if someone tries to break inside.
The reason for all the security? Because Centcom
do not like it when people steal money from them. whenever a certain amount of gold is taken from the vault, every buddy and robot on the station goes nuts and the AI/Borgs get a new law 0 of "Retrieve the space gold, this overrides laws 1-3"
All kinds of new, fun ideas can spring from this! Traitor objectives to steal the gold, obviously, but you can also do stuff like sticking a briefcase inside the vault for spies to fight/backstab over. Give the crew objectives to fill the vault with extra space gold from mining, trading, or exploration. Allow space gold to be used to bling out accessories, so rich traders or clever thieves can flaunt their newfound wealth. Clever traitors can mastermind an unnecessary heist, to cause havoc on the station and disguise their true objective. Or at the very least, it could be used as a gimmick for admin-shenanigan rounds.