Philthy,
IMHO ADS-B should be compulsory for all aircraft where VHF is required to be carried.
The kit allows other people to know where you are in the event of your radio failing, you being on the incorrect frequency, you being lost, you giving an incorrect position in a radio broadcast etc. I believe the Commonwealth has a duty of care to advise other users of its Airspace in such events, it would also reduce radio clutter.
As for cost...I saw at one stage ASA were looking at installing it at their expense in all aircraft in Australia as retrofitting every aircraft would have been cheaper than the planned radar upgrade.
I also believe the Commonwealth Air Navigation Act is sufficiently broad to charge all aircraft for use of the Commonwealths’ Airspace and facilities. IMHO that will happen sooner rather than later.
