I do not know , if they have ammended the constitution , NZ would make a good fit as another state for Australia , they have lots of water , lots of cuddly sheep , birds that do not fly that are probably easy to catch and eat , soft commodities like Dairy and forestry that are a good counterbalance to Australia's minerals , the older generation of Kiwis are well educated , (younger ones not so much ) .
Only problem I see is some parts of the country probably still have native tribes that may still be uncivilized , call them selves the mongrel mob even , how would you get them to integrate in society as the Aboriginals also have the same issues ?