As another Kiwi thought I'd throw my 2 cents in as well.
Sometimes it does seem like there is a bit too much positive discrimination for Maori in NZ, but really how much does it actually add up to? A few parliament seats and some scholarships, not really enough to bother me that much.
And since I come from the South Island how about this for an alternate history, a much bigger South Island movement?
(There actually is one but it is very very tiny)
http://en.wikipedia.org/wiki/South_Island_Independence
So would the South be New Munster while the North was Aotearoa?
How about something along the lines of a federated Empire and a different commonwealth?
The King/Queen of Britain would also be Emperor/Empress of the Empire. In cases where the nation in the Empire abolishes monarchy, the Emperor/Empress will be Captain General over a President.
So, any nation in the Imperial Federation can choose;
1. Have the British monarch as head of state, represented by a Govenor-General.
2. Have its own monarch as head of state, with the British monarch as Emperor above that monarch.
3. Have its own president as head of state, with the British monarch as Captain General above that president.
The New Zealanders can then chose to have a Maori as their monarch (butterfly in a high-ranking royal blood maori that has commanded in ww1 and perhaps gone into politics and is widely popular and seen as a threat by those who don't like him - giving him a ceremonial position will neutralise him) that will be King of the Maoris and Duke of New Zealand (or whatever title is worked out - Imperial Prince, Grand Duke, Archduke, King etc).
There are several examples of formerly British territory becoming constitutional monarchies in mainly 2 formats:
1) Places like Jordan where the Hashemite Monarchy (local to the area) was put on the thone by the British.
2) Places such Bahamas/Canada/Australia/NZ who have gained full independance, but still retain the British Monarch as the Head of State.
Since New Zealand achieved it's own independance and awarded the New Zealand Crown to Elizabeth II, it's ASB to suggest they will just wipe away the rules of royal succession in order to change royal families. Especially in NZ.
Although.......I do sometimes wonder what would happen if Prince Charles' siblings who - let's face it - aren't going to inherit the crown, moved out to the realms. For example, have Prince Andrew move out to Canada 20-30 years ago...would Canada consider jumping over Prince Charles in the line of succession in order to have a local Canadian Monarch instead of a Governor General?
Interesting thought but still ASB. NZ, while one of the last dominions to have a national identity, certainly had it after WWI and Gallipoli, so a federated empire isn't really too plausible, but a Maori leader of NZ is definitely not. It's got nothing to do with race either - there's just no way, especially in the 1930s, that the white majority of New Zealanders will elect, select or allow a 'native' leader. It's barely even plausible today. Especially in the South Island (which had basically no Maori in the 19th Century, and barely any in the 20th).