Correct me if I am wrong, but i cant think of a single registered aerodrome that doesn't have at least one gnss approach. Most will have 2 by the end of this month.
There are now at least 5 other organisations certified to provide instrument approaches in Aus.
Yes it would be possible to develop a criteria for gnss guidance arrivals in Australia, criteria only currently exists for conventional azimuth guidance. Note these are not icao procedures. The new critetia would require extensive safety work and testing, again not impossible. The roadblock is casa's insistence that we only design approaches to icao rules. They are not interested in developing any new Australian rules