Culture is my favorite victory, and I was on board with new amphitheater, defensive UU to let me ignore other civs, and the unimproved tile bonuses since I think National Parks are cool and it really encourages those. Plus being able to scout for your capital is cool, and ideally you can settle near a natural wonder for that sweet tourism come National Park time!

But I’m lost on a lot of the things you mentioned. First of all, I know nothing about the accuracy and flavor of this civ for the Maori, if it’s fitting or not, but the abilities look cool on paper. No Great Work Slots in the Amphitheatre is a bummer. But no Great Writers? That’s a letdown for me. And I agree that Mana is too complicated. I would remove the embarked unit benefits, change bonus yield to unimproved forests and rainforests to only rainforests, and remove the culture bomb from fishing boats. Maybe allow for harvesting of resources or not depending on the civs balance at that point.

I’m no expert though, this is just my semi-casual analysis as a lover of the game, I am no guru like you!