CASA is the national airspace regulator, and they manage that via their Office of Airspace Regulation.
Amongst other things, it is CASA OAR who decide what class of airspace is appropriate in areas and what level of air traffic service is required at particular aerodromes, and issue directives accordingly. It is they who declare by legal instruments most of the airspace types in DAH.
https://www.casa.gov.au/operations/s...page/about-oar
With my last dealings with their Operations side they didn't seem to have anyone with any
civil experience in airspace design, airspace management or ATC experience, just ex-RAAF ATC of quite some time back.