It's not particularly hard to find people serving 5+ years in US prisons who one could gamble are no more or less a threat to society that the average person.

Having said that, I could make you the same offer, except I choose for you a as-of-now non-offending police officer, corrections officer, doctor, fireman, military service man or other upstanding citizen, for whom who will take life-long responsibility. If they commit a crime your penalty will match theirs.

If that doesn't sound super appealing, it might have something to do with playing Russian roulette, rather than an argument against rehabilitation.