*sigh* I would dearly love a south african Armadillo Lizard, or one of those cute little hognose snakes, but I know why the laws exist, so I will continue to dream. Or maybe go do a photo-sufari looking for them in their natural habitat instead.
The fact is that Australia is unique with it's wildlife. The continent has been separated for so long that our wildlife is not really on the same evolutionary level as most of the world. Our mammals (with the exception of the dingo which is a feral of old) are marsupials and even monotremes, which are rather primitive compared to placentals. They couldn't compete with cats and dogs.
Even our reptiles are a bit behind compared to the rapidly reproducing, hardy corn snake and ball pythons, which although it doesn't mean I think they are inferior, it puts them at a distinct disadvantage.
Can you imagine what would happen to our wild jungle python and green tree python populations if we had a feral population of tree boas? These snakes are at a distinct evolutionary advantage, because they give birth to young ready and rearing to go! Far less vulnerable than eggs!
How could our coastal carpets compete for food and space with boas?
How would our water pythons compete with the humumgous anacondas?
It just wouldn't work. Of course I can't see a feral colony of Galapagos Tortoises getting out of controll and rampaging across the country, you can't really have one exception to the rule, it's easier to enforce a blanket rule. JMO.