Lead, your last questions expose the myth that is Australia airspace policy.
The last published assessment of Ballina airspace by the Office of Airspace Regulation, is 2015. In it they said that the airspace (Class G) was fit for purpose but recommended a CA/GRS (Class G with a directed non-ATS traffic service!).
Now, according to AIP Supp H140/19 that arrangement is no longer fit for purpose because four VFR pilots failed to make the transmissions required under CAR 166C. So CASA introduces a Broadcast Area (Still Class G with a directed non-ATS traffic service) which is not an airspace change, it is a radio procedure change that eliminates non-radio equipped aircraft.
The AIP SUPP however only requires that pilots (not aircraft they are machines) make a radio call when departing, entering or transiting the broadcast area. This is essentially identical to CAR166C minus the "if the pilot has a radio" part.
As I have written previously CASA has run out of mitigaters to reduce the risk at Ballina - the probabilities of a mid-air are addressed in the AIP SUPP by stating that the number of movements are unchanged at 13,000 but the number of air transport movements has decreased by 12.7% so the risk has in terms of likelihood has actually reduced!
Now I am not arguing that nothing needs to be done, there is clearly a problem, I am only arguing that CASA does not seem to have the balls to tell Airservices to install some surveillance or impose positive air traffic control over the airspace in order to safeguard the fare-paying passengers.
I would only add that if these separation issues are coming from the airlines flying into Ballina, as I suspect they are, they should think very hard about whether they need to risk their reputations by using this particular airport.