It's not just in Australia, the FAA is still trying to nut out the problems with high traffic CTAFs such as in Alaska, where there have been multiple mid air collisions. So far the only thing working is when all aircraft have some form of ACAS/TCAS fitted, yet all agencies seem so reluctant to mandate working transponders in these areas. The last major collision was between aircraft where both had ACAS, but one had it switched off. Yes ADSB can be swamped but the system tends to prioritise close contacts so that means that unless you have 18+ aircraft within 5 miles it should still work fine. Class D can not work in the Ballina area, its way too complex to efficiently operate a tower there and blocking out airspace for CTA will then condense the VFR private traffic even further creating more risks for them. Move into the 21st century guys, get transponders, use them and its all good. As for separation standards in class G, don't collide, sounds great, but TCAS applies a bubble around those fitted so when you sneeze close to each other you get an RA and that's a mandatory report to be investigated.