My second level of concern is that it's a civil penalty on top of a criminal conviction. You're losing something. The state is taking away a benefit that you previously had. Where other people who might be equally at fault may be in the first category--maybe it was a self-induced injury, or something like that where there was an element of fault--they would be entitled to the deferment, and the other people would not.
What you're doing is you're looking behind the reason for the incapacity and you're heaping on another penalty on top of the conviction, which amounts to a deprivation of liberties in association with a conviction. The entire deprivation of liberties should be the penalty that is imposed by the sentencing judge in connection with the offence that's committed. Otherwise, you get a very uneven and unfair problem.