OP dude, this is a bad idea and would never work. The risk to Mt Gox would be way too high for them to even consider it. Think harder, say we have the protected $50-$60 range as you say, if some seriously bad news comes out, say protocol is compromised which means the true value of bitcoins should be $0 (but information leaks out slowly), then Mt Gox will run out of cash no matter how much they have. They would need $60x11m to be absolutely safe to buy all outstanding bitcoins. Then the owners have lost half a billion for no reason at all. If the Feds say tomorrow they will accept bitcoin for payment of taxes, the next moment all of Mt Gox users would stampede out of there to try to get higher prices at other exchanges, need I go on?
If Bitcoins go to $0, do they really care? There's no more exchanges in that case. They declare bankruptcy. Liquidate the assets. Companies go broke all the time. If losing millions was a crime, we wouldn't have any corporations left. MtGox is tied to BTC, sink or swim. They might think this gives Bitcoin the backing/stability it needs to go to the next level.
There isn't a bank in America that has the cash on hand to handle everyone withdrawing their balances. The banking industry is legalized gambling, but MtGox wouldn't stoop to that? I don't know.