3 things come to mind immediately.
1. The 767's that Airnz used were not RNP capable, so they would have to use the higher approach minima like the ATR's do now (Cowpatz may prove me wrong on the RNP part)
2. Runways isn't long enough to make it economically viable to take them there, and also there is no turning bays at the end of them for it to turn around (such as Dunedin)
3. I don't think the apron is large enough for them to park there.