MULTICOM 126.7 MHz procedures be recommended for all operations at low heights (below 3000ft or 2000ft AGL) in Class G airspace when clear of established CTAFs and Broadcast Areas.
How is that going to work around the major CTR/CTAs e.g. within 15-20NM of Melbourne?
The CTA LL being 2500 and lower means that aircraft will no longer be on the FIA and therefore would be uncontactable by ATC in the event of penetrations of the CTR or CTA (check the link below, "Airspace Infringement Hotspots"). Also unless dual VHF, IFR will be out of comms with ATC if proceeding through Class G airspace, thus no SIS or SAR.
I recall someone at the Victorian RAPAC was once pushing for a broadcast area which would do the same thing, and the proposal was rejected both by ATC and CASA for these reasons.
Airspace infringement | Airservices