You are aware of course that the EU and UK have expected international businesses to register for and pay VAT on any sales to EU and UK citizens for decades right? You can't shut the barn door, the horse has not only bolted it's managed to catch an international flight and make it to another continent.
This works fine within the EU, because there are agreements in place. It is my understanding that the current law does not permit EU countries to pursue sellers outside the EU who don't charge VAT. If goods arrive without VAT being charged, the importer is liable for the tax. That's no different from the current situation in NZ or Australia. What is different is what the ATO says they will be doing - actively trying to force non-Australian businesses to comply, and pursuing matters through foreign courts.