I suppose the best solution is to take him out on a mission and have him shot from behind by another soldier....
Nah, I just ship them to a small manufacturing site at the south pole as a security guard in case of invasion. In the original, I seem to remember you had to have at least one soldier in a base to be able to fight off a base invasion even if you had a bunch of tanks, wounded soldiers would work as well. Not sure how that stuff works in openxcom yet.
The lighting rod idea is notable, and the 'real life' joke was nice. But really it would be nice if units who shoot their own team would be demoted, or put on administrative leave. And mind controlled units might need counseling as a different type of wounded.
It would be nice if there was a medikit kiosk in the aircraft, sort of like a medicine cabinet that an injured unit might be able to use by themself if they're able to get back there in time.