Pottering through Casa's airpsace design manual
A C 2 5 1 (as you do on a Sunday night...) I found this little gem:
15.4.1 Class A airspace is not intended to provide a higher level of safety than Class D airspace per se.
Which would indicate that OAR has Ledsled working in their drafting team.
In fact, the whole of section 15.4 (Cost Benefit) is farcical. Class D not appropriate for Melbourne. You don't say.