and just to roll a hand-grenade in ...
What about an allowance covering total weight of: passenger + checked luggage + carry-on?
Passenger stands on scales with "all" their bags and coats and ... whatever else they are carrying onboard. No weight shown only how many points (using Roger G's idea) earned ... or lost?
Aside from logistics, time, customer pushback, infringement of 'rights'. any other issues to stop this being done?
Time is the issue with me. Getting to the taxi queue before my fellow riff-raff saves considerable time.
Disclosure: just a passenger of below average weight mostly on day trips with a small backpack who is a bit pissed off with the volume brought onboard ... and just a bit concerned about the (unknown) weight of it all.