Delta will actually start doing exactly what you asked! Starting on a limited basis: if you are the only traveler on your PNR, are already indicated as checking a bag, and one of your flights is booked to the point where agents would have to solicit gate checked bags from passengers anyway - you’ll be able to check that gatecheck bag at the ticket counter. Should be a smart way to limit the amount of gate checked bags required and help speed up security with less bags to go through the machines.