Anyone who wants one is given a ribbon or strip of cloth, say 1 foot long by 1-2 inches wide. One side is red, the other side is green. A ribbon left on a seatback with the red side showing indicates "I am away just for a quick beer, bathroom, or smoking break, please don't take my seat!!" A ribbon left on a seatback with the green side showing indicates, "I am away for this set - either in the lobby or down on the floor. Please use this seat for this set, I'll be back when it's over!!"
These ribbons would be available to anyone who wants one, but there are probably lots of people who plan to be on the floor most of the time and wouldn't need one, they'd be the people occasionally looking for a "green" seat to take a breather. Gold badge holders would still have the perk of early admission for best choice of seats. I'll bet a sponsor could be found to pay for the ribbons / cloth with their name and logo all over it.
There, I have solved our problem.
Ken