First the NZ regs. Local engineers seem to be running scared of designing and certifying tow rigs for modern cars so he have a large number of toweds on the road that are basically unsafe to drive. - no airbags poor steering and braking safety. - Note the current car safety adverts advising you to think again about driving cars incapable of withstanding (surviving) even moderate crashes.
In Australia you have many choices of certified towing systems for late model cars and, indeed, if you attend a CMCA rally over there you will find dozens of examples of different setups. The chink in NZ's regulations is that we recognise Australian engineers certification so you can use properly certified systems in NZ. The problem is that they cost. You won't come out with much change from Au$3500- it could be even more now.
If you do opt for this then have it installed by a NZ engineer and notify your insurance company you will be towing .
I was approached by a traffic cop several years ago while I was disconnecting the car and was told the setup was probably illegal. I keep a copy of the certifications in the glove box and gave them to him. He went back to his car and kept me waiting for over 20 mts while he talked to someone on his radio and finally came back and said all was well.
Talk to Northcoach in Queensland.