It appears that much of the talk re Badgery's, Wilton, etc. is for an aerodrome to replace KSA; likewise much of the talk around RIC & Willy (such as teh RAAF study quoted above) appears to be for them to become 'major' civil fields.
We have to assume that KSA will remain the primary for years - decades - to come. But could not RIC and Willy become - not major civil fields, but overflows?
Riccy could have a limited number of A320 / 737-sized, short- and mid-range services, meaning no runway extension, limited impact on military operations and a viable alternative for anyone north and west of Parramatta - even if available destinations were only (say) MEL, BNE and ADL (and the odd AKL perhaps). Stick a cat III in and the fog issue is largely addressed.
As for Willy, the Newcastle / Hunter area has sufficient population to act as its own catchment, and it is too far from Sydney to be a 'second' Sydney airport - again naturally limiting ops to the extent that there would be no threat to mil ops.
So if each of RIC & WIL took 10-15 services a day, that's 30 slot pairs a day opened up at YSSY. Even 24 services between 06.00-18.00 would be only 2 arrivals and 2 departures per hour - one every 15 minutes - would that seriously stuff up military ops?