CASA's argument, as put to me by the head of avmed, was that DAMEs would be exposed to much more liability and thus have to charge more to cover their insurance, if they were to issue their own medicals without the intervention of AVMED.
The head head of AVMED really believes this, then I have a nice bridge I could sell him.
Seriously, if he has such little understanding of PI insurance, then he demonstrates that he in unqualified for the job. Does he seriously think that private pilot medicals are the highest professional risk activity that doctors perform? I doubt it would even make a list of the top 20.
I also think you are out of date with the Australian DAME training. And lets not forget that these are pretty highly trained doctors to start with, who in their practices deal with a range of other medical certifications, from drivers licences, boat licences, SCUBA medicals, to the employment medicals for fire fighters and ambulance officers.
In heyday of GA, there was no DAME training. In the 70's & 80's the DAME list was pretty much an old boys club.
The forsyth review is here:
https://infrastructure.gov.au/aviation/asrr/index.aspx