You are committing a common error in portraying the Māori and their culture as being crushed and suppressed by colonialism. Hapless victims. The reality of the interplay between missionary and Māori is far more nuanced than that and you a strong disservice to Māori in your portrayal.
I'd ask what basis you have for your assertions about the 'lost' definition of mana, when the definition of mana in the Māori Dictionary specificially states:
> 2. (noun) prestige, authority, control, power, influence, status, spiritual power, charisma - mana is a supernatural force in a person, place or object.
It goes on to explain how mana originates from the Atua and propagates down. It also discusses the close relation between mana and tapu. http://www.maoridictionary.co.nz/word/3424
However, I do believe that Maori history and cultural perception has been colored by Christian historians. This has only recently begun to be rectified by John Moorfield, and other authors who have contributed to the Maori dictionary, which is a relatively recent advance.