So if that's the case, then the heavy-handed stuff obviously didn't work with Mark. Cut him a deal to reopen MtGox so everyone can get on with their business. He's smart enough to realize he can't steal everyone's coins and still get off completely scot-free. Let him keep 10% and have a get-out-of-jail-free card in exchange for giving up the rest of the stash. 10% should be plenty to keep Mark in frappuccinos and Tibanne in kitty treats for the rest of their lives.
Interesting thought; the real question here would be if you'd trust such a guy with your money / bitcoins ever again... I'd certainly prefer to burn them rather doing that.

If he's as guilty as most people surmise and has an IQ above room temperature, which he does, then he'll simply take his 10% and run. Plastic surgery could compliment his new more svelte appearance so that he'll be able to enjoy his winnings in unchallenged obscurity. Purple or chartreuse highlights could help disguise Tibanne.