This is what I am saying. When you walk up to the counter, they weigh what you are carrying on, what you are wearing, and what luggage you are checking and give a total limit. Have charges that have tiered factoring. If the total is 350lbs, the factor is 1X for the ticket. If 450lbs, the factor is 1.5X for example.
This would give a LOT of incentive to slim down and pack less.