Can you do a "1-of-1 or 2-of-2" transaction, where either the overseer spends the coins, or both the overseer & the holder spends the coins?

I could open an account with the overseer & use a non-bitcoin currency, but you would lose the bitcoin's benefits of the inability to arbitrarily mint new currency, and the public transaction ledger. ie. if they stole it you would know immediately.