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?
You can do 2-of-3 (overseer holds 2, so can always spend, you hold 1) instead to accomplish the same thing. I suppose having the overseer put transactions in the block-chain that everybody can see might make you and the people you're paying trust them more...
Thats an interesting way to do it. Might as well just give your coins to the overseer though as they don't need you. Maybe have 2 separate overseers? Seems strange and I'm not sure I see a use-case.