Either support or don't have an opinion on most of your list, but will comment on the following.
VFR aircraft are restricted from operating above FL200 in Australia.
No they are not, but a badly expressed rules says they can't without CASA approval. CASA grants such approval if the aircraft is fitted with an IFR calibrated altimeter. They have also permitted glider flights without such, including class A airspace, subject to LOA with ATS. I agree this is a silly rule though.
No similar restriction exists in North America. There are times when an aircraft could fly at FL245 and save enroute charges and fuel.
Erm, not permitting flight above FL180 is an improvement over there hey????? The NAS changes are a bigger impediment to VFR access to high level airspace than this rule. Prior to the NAS 2B changes VFR could get a clearance up to FL285. Now they are permitted (subject to the above), but not in the class A base FL180 environment that coincides with the best radar coverage in the country - the area best able to deal with such flights. This is also the airspace that most closely resembles the US model, do you want to roll it back to class A with a base of FL245? If so, do you have any inkling as to what you will be demanding next week?
In Canada and the UK, an aircraft can fly IFR in Class G without a directed traffic service and not pay an enroute charge. Australia should harmonise with this as per the NAS policy.
I thought the NAS policy was to have class E airspace corridors 4 nm wide with a base of 1,200 FT AGL, and down to 700 FT AGL in terminal areas anywhere an IFR aircraft is likely to make an approach. The knock on for this in the US is no IFR aircraft can move anywhere without a clearance. Where do you envisage IFR exhibiting these wondrous freedoms, or is this more rollback? Isn't this the core of LLAMP you fought so valiantly against a short time ago??? You could have had this already and it is partly your fault it has not happened.
Larger Class D and Class C airspace around Australian towers means that greater diversions are required by aircraft avoiding the airspace.
The justification in the US documents for their skimpy terminal areas that aircraft within constantly brush the edges of is that they are separated with any IFR aircraft in the class E airspace surrounding. Reducing the size of D & C airspace without the mitigators present in the US has the potential to decrease safety, particularly with your 'free in G' mates happily brushing the other side of the boundary.
Do what you like to the vertical extent of such airspace, I'm sure OAR will prove it is safe before they implement it.