Even Christchurch to Chatham Islands is 470ish Nm so you would probably struggle to 'Air Deploy' to all parts of NZ if it was blowing more than a light Easterley.
Really? I've had limited exposure to ADF MRH's and thought a ferry leg of this length would be possible with addition fuel tanks (external/internal). Don't know, but when talking payload/range with crew that was the impression.