How about a simple rule? “No entry to a ten mile circle below 5000 ft without operational transponder and radio. The radio to be tested against the afru?” That should go close to guaranteeing GA and RAA aircraft or sqwawking and on frequency.
Personally, I’ve noticed that some circuit traffic makes a full stop and waits when RPT announces their imminent arrival. Unless I’m close to fuel emergency level (which,is never, so far) I always defer to RPT. Maybe a rule giving RPT a ten minute window might work. No GA operations within the window?