Back to the missing Bitcoins and the original question. Identify the Bitcoins and stop them in their tracks. Whether double spent or stolen, mine are mine and if MtGox sent them to someone else that's theft.
You're not a newbie based on the post count... you should know by now that what you suggest is impossible.
non-sequitur
But why not stop those bitcoins from being traded ASAP. If somewhere down the road a decision is made that the stolen/missing Bitcoins belong to the rightful owners and those transactions with stolen/missing Bitcoins are not valid then freezing them now would limit the damage and to argue otherwise aside from arguing as the devil's advocate is suspect. A pain in the ass for the blockchain yes but better sooner than later.