Nah. If they request euthanasia, it puts an end to them being miserable.
With the size of him when he went in and the lack of activity/crap food since, a few extra fry-ups are probably contributing towards a case of type 2 diabetes with all the painful complications that involves if poorly managed by the person with it - other high profile prisoners there have been reported as having them, after all.
I'd chuck him a giant Toblerone each week for not being quite as much of a bastard to everybody if I thought it would help give him a gangrenous foot or two. And no euthanasia if T2 led to unbearable neuropathic pain. He won't be enjoying a bit of Fifa anymore if he can't see because he's lost his sight, either.
No need to risk making mistakes with other people through executions - he's got the means of making his life utter misery for a very, very long time this way. He just doesn't know it.
<shrug>