When I was 18 I ripped a load of my Jaw muscle, weirdly by yawning. Now even touching the muscle can hurt on a bad day, but to be punched in the side of the head theres just no way I would be in horrible pain.

If it was not for that I would love to train just to help me get fit and work on my muscles and reflexes.
But to do all that and not be able to spar just seems a waste of everyones time really, they'd be better off giving the gym space I'd take up to someone else.