Squawk 7700,
At the risk of being pedantic, two of the accidents you mention were on the ground, I trust you are not suggesting ADS-B should be used to see if the runway is clear for takeoff or landing.
As for the rest, you have the "wonderful" example of the Australian approach to "organising" traffic to unnecessarily increasing collision risk by concentrating the actual traffic in narrow lanes, eliminating to a large degree the "big sky" level of protection.
Having said that, the accidents quoted are statistically meaningless without rates, and occurred over many years, and all had one thing in common, they occurred in areas where ADS-B will not substitute for the Mk.1 eyeball, for the primary (but not the only) reason I have already mentioned.
I would seriously question the sanity of any pilot who suggested that you need ADS-B to tell you that you are likely to find traffic in and around an airfield, particularly a capital city secondary airport.
I have many years of experience of TCAS, from its earliest days to the most recent and greatly improved most recent versions, there is a bleeding good reason why you normally disable the RA functions in the approach area.
Like TCAS, ADS-B has the capacity to become a major distraction to a good lookout in and approaching the circuit, thus increasing risk, not decreasing it, which is exactly what studies in US have already found.
As I said originally, spending the money on making certain your low speed handling competency is right up to scratch is far more likely to reduce risk --- produce a "safety" dividend if you prefer the S word.
As uncomfortable as many aviators find it, facts are facts.
Tootle pip!!