By saying that it could place a burden on industry, implies that ultralight training is an industry, a commercial operation. Therefore requires an AOC like the rest of us.
I'd be interested to hear peoples thoughts on an alternative to AOCs for GA schools. For example, what procedures would be suggested to ensure that all flying schools trained to the industry standard, ie the Day VFR syllabus, if CASA chose not to be involved. Who would decide what the standards are? Who would justify the potentially enormous loss of jobs in the established industry? What controls would there be over all the enthusiastic but unsuitable people who might fancy setting up their own flying school? If it was all run "el cheapo" then instructor's wages (if there were any) would suffer, and the next generation of airline pilots...where will they come from?
There was discussion previously that having an AOC would impose huge costs. Not so. I calculated then that my AOC costs 0.0003% of my annual turnover. It's not that hard or expensive if you know how to go about it, and if you don't then it's not too hard to find out, if you don't want to do that then don't bother.
IMHO there should be one licence to fly, just as there is one licence to drive, and the training and testing should be the same throughout aviation. Not a mish-mash of exemptions.