I think that is a brilliant idea! Pay for carry-on luggage.
Delta never told me my carry-on would go to the carousel when they tagged my bag in ATL. So I get off the plane at FLL and stand around by the gate waiting for them to show up with the usual hand cart of excess carry-ons. Nothing happens for several minutes. I noticed a TSA agent eyeing me suspiciously so I went to the desk and asked. "Oh, they just put all those in with the regular checked luggage. It'll be down on the lower level at the baggage carousels." Visions of my $300 leather roller being carted off by someone passed through my mind as I raced down to the lower level. Let me tell you, I was hot, and not from exercise.