Sliding scale plane seats

This idea was going to be an anno under a recent "fat folks pay more to fly" idea (linked), but that one was appropriately marked for deletion, being a rehash of a similar idea from 2001 (linked).

For plane flights, there should be a sliding ticket scale, and chairs should be adjustable to fit the occupant. Consider the large passenger - on sitting in the sample seat he takes up 120% of a typical seat. His seat is adjusted to accomodate and his ticket price increased accordingly. Consider the mother with two daughters. Each daughter takes up only 75% of a normal seat, and so their seats are reduced in width, along with the price they pay. An additional 75% normal seat could then be placed in that row. Little kids and very slim folks would pay substantially lower rates for their narrow seats, and converse would be true for the very large. This would be helpful for families travelling with the very old and very young, as these relatives would now be cheaper to bring along. An average person preparing for an expensive $2000 plane trip would have incentive to "make weight" and slim down, hoping to get a 92% normal seat with a corresponding $160 savings. Passengers would also tend to keep pockets empty and wear control girdles, which could be available in airline gift shops.