Hey swh
"There is no 737NG's on the NZ register so it is impossible to hold a 737NG rating on a NZ licence."
I have NG on my New Zealand Licence and have had it 2000....so you revisit your rule book guys. The NZ CAA arent making it difficult...they are saying that Boeing is the only ground school they currently approve. Its not rcket science! how many conversion schools around the world do they have to sit on to satisfy everyones budget.
There may be other ways...think outside the box. I had to and it worked. Look at the TTRMA and other NZCAA approved licences. If you really want the Ng on your NZ licence you can do it. I did it ...I used it.!
Good luck
morph