For instructing in NZ.... a cambered directional carving ski. Volkl Racetiger springs to mind.
If you can only have 1 ski... that makes it tricky. Which part of NZ are you heading to?
You probably want something rocker-camber, twintip, not overly fat or all your demos will be kinda weird because obviously you ski a 120mm ski kinda differently to Joe Bloggs on his 75mm rentals.