Dick,
I had a look at the US airspace model you posted Dick and noted that Australian NAS has different levels of service with different volumes of airspace. For instance, why do the US only have Class G up to either 700' or 1200' AGL and we are looking at more than ten times this upper level? And so on. Call me simple, call me stupid, but we do appear to be replicating the system but morphing it to suit some arbitrary design rules. Not against reform but either we implement it the same or do the full Monty on it.