I think the brain injury issue would be a much bigger hold-up for him than a prosthetic leg. Sounds like he has limited function in his remaining leg as well. I hope he gets a shot, but brain injuries are real hard to overcome I believe.

If I am not mistaken, the FO on that FedEx plane where the crew was attacked by the jumpseater had a brain injury - i believe he has lost his medical forever - can't even do the light sport thing in an LSA.

Good luck to him!