The British were coming into a country that they hadn't been to before, and started going crazy. With all the lawlessness around, the British decided to make a treaty, and what did they do? They made one, yes, but did Maori have input into it? No! So they should have because it is their land, and because there are a lot of tino rangatiratanga (Chiefs), that wanted the land and food back from the lawless British. Maori chiefs that were at the signing at Waitangi, e.g. Kawiti, Heke Pokai (Hone Heke) and Marupo. These are some of the chiefs of Nga Puhi.
To a conclusion, YES Maori should have had input.
P.S. Note that not all British were lawless.