I had the same problems and also questioned the stamp duty on one of my personal imports for QLD and even though i also had proof the vehicle was previously registered in my name they said it was irrelevant as it is new registration and its just a tax i have to pay. this would be the same in all states for stamp duty. I would sugest you just state a price the car was worth to buy or sell in the country you imported it from IE the lower the better = less stamp duty.
Queensland i believe atm has 1 of the most relaxed registration laws in Australia apart from WA, you will need RWC to register it in your name but then you just need to keep paying registration no more RWC unless you sell it.