What I would be concerned about is what is defectable in each state. For example, if you had an exposed (but solidly mounted) pod filter and drove to Melbourne for a holiday, could you cop the $600 Victorian fine for having an exposed pod?
Or what if a NSW car has nitrous lines and nozzles (but no bottle), and drives to QLD for a holiday? Will they be going home on a tilt tray for something that is legal in the state of registration?