I don't know why we're playing this game with Dick again, but it's like lighting a flame in front of a moth.
I've looked through every book and manual and standard and publication on the matter - and nowhere - not anywhere - can I find any reference to the need for radar to provide a Class C service. If that were the case, then you'd most certainly need radar for Class A airspace - and that would mean putting radar through all the upper airspace in Australia.
On the subject of risk, if there is a certain level of collision risk between an IFR aircraft and another aircraft in Class C airspace, with all traffic known, and all traffic positively separated, then there is a higher level of risk in Class E airspace to that same IFR aircraft, where not all traffic is known, and not all traffic is positively separated. This is an INDISPUTABLE statement - even you can work this out, Dick.
That's not to say you actually need Class C airspace - it's just that we want you to admit, Dick, that for the same volume of traffic operating in any given airspace, the level of risk increases as you go from Class A to Class G.
Having admitted that, you'll get most of the contributors here back on side.
Then you need to convince CASA to FINALLY bite the bullet and actually determine what level of risk they're prepared to accept - then find an airspace classification that matches the risk.
It's not rocket science - surely the overpaid bureaucrats at CASA, after so many years, can be forced to at least give us an acceptable risk number. Everything falls into place after that. Airservices can staff accordingly, systems can be adjusted accordingly, training can be provided accordingly, and you FINALLY get what you want - risk based services.