Isn't it about time that passengers over average weights were charged a kilo rate for every kg over the average - and come to think of it, those under average could be given a discount.
Just need a cubicle beside each check-in desk / self check in machine so that the surcharge / discount could be calculated and collected or divvied up.
Can't seeing it being overly popular amongst the PC brigade - but can see Jet2 doing pretty well out of it!