Let's face it, you can drive everywhere in NZ pretty quickly 
?&^&*??
Auckland to Gisborne is a what 6 or 7 hour drive, or a 50 min flight.
How about Wellington to Christchurch? That's got to be 8 hours including the ferry.
I dont know if either you don't live in NZ or just haven't been south of the Bombay hills for a while but the difficult terrain and relatively small population versus land mass area surely make this a country very suited to air operations.