They are getting some flak on this, but are they listening?. Maybe. Maybe not.
I posit the following compromise, for those that reckon 20 nm too big, and those that reckon 10nm too small.
1 The CTAF radius will be 15 nm
2 the lid will be 4500'
3 the strict liability penalties will be calculated on the basis of your height and your distance from the 'drome when you made a 'faulty' /non standard radio call/ their allegation,(either unsubstantiated or untrue) and you can spend a bundle contesting that or spend a bundle paying the CAsA's claims. Your call.
Probably best that your radio 'fail' 22 miles out and just keep a good look out and listen carefully. Safer and MUCH cheaper.
2c