A key issue with transponders is that gliders don't carry enough power to run a transponder. Some gliders don't have ANY onboard electrical equipment. Mind you, it does mean that the carbon footprint is rather small!
Fine, ban 'em from all controlled airspace, or any of my Mode-C vales
Which is what may happen in reality.
"Hello Bourenmouth, Hi, yes I would like to do a bit of gliding in your controlled airspace....No, I don't have a radio, no I don't have a transponder, you see we don't have any electrical equipment onboard....why? Because we don't, and we don't feel that as gliders we should have to fit any....what do you mean bugger off?........"
