You could do the oral with an Aussie Flight Examiner by Skype, if the Examiner accepted that (as I see nothing in the rules to say an oral means 'face to face'). The problem arises with the Examiner having to sight the candidate's medical and placing a signature on the licence. That stuff can't be done remotely. So, at some stage of this process you would have to present in person.
I agree that CASA seem to stress more about whether pilots know the rules than whether they can actually fly. If they cede control of the flight test to foreign ATOs on trust, surely they could allow the foreign organisation access to a question bank?
Or better still, require the questions to be done on line. At least that way we would get some consistency in the way the rules are interpreted and a guarantee that all the questions are actually asked and answered.