So Dogs_ears_up,
What would you do when you have a passenger so tall that he can't sit in the seat? Do you throw him off the 'plane? If so, how do you handle the resulting legal claim because it's more than likely there's nothing in the conditions of carriage about people being more than a certain size not being carried - and if there was, it would quite likely get heavily hit in a discrimination law suit?
It seems to be one of those cases where npobody is likely to win except a lawyer.