but prior to the recent change
The AIP amendment came in 2 years ago - mid 2013 - I don't call that recent - and at that time CASA said that change to make AIP clearer was consulted to the industry in 2009 -
The AIP is clear as to what frequency to use. As I've said - its not rocket science, and the pilots and instructors I associate with understand and comply with it.
Trying to impose a multicom across the whole country up to (say) 3500FT but of necessity needing it to be clear of CTR/CTA/CTAFs/Broadcast Areas/PRD would present its own safety issues and just complicate things further IMHO (and of course, would need a HAZID and safety case).
Captain Nomad: I concede the point you raise, however in those regional areas in most cases the common frequency is for Class G and Class E not the overlying Class A, where it is claimed light aircraft transmissions in Class G might jam a jet's call to ATC or vice versa and cause loss of life.
I don't believe the problem is as big as being made out to be, and as said, if the chatter proves to be a problem in an area or location then there are measures able to be taken.