Not to mention, what happens in the event of damage to the towed aircraft rendering flight operations impaired such that it affects the towing aircraft?
Unless "affecting the towing aircraft" means "ripping its tail off", in which case you're screwed no matter what height you're at. GA aircraft are probably a bit sturdier, but large cargo aircraft (based on large passenger aircraft) were simply not designed to pull anything, so I imagine you would need to add some kind of (pretty sturdy) reinforcement to the attachment point, which would mean extra costs and reduce the MTOW of the towing aircraft.
“Oh sh1t!” at 35K feet.