It'd be nice to scrap it in favour of a new one, and incorporate Maori too.
The only problem I have with such a move is the same problem I have with NZ becoming a Republic: I don’t have enough faith in the powers-that-be to not fuck it up and we end up with something worse.
As for Maori language in general. The older population have some vastly different attitudes from many of us towards compulsory teaching of the language. I find the differences more interesting than anything.
Here’s (just) one highly practical argument for teaching Maori language though: Learning more than one language enables our brains to learn more languages easily, and, when you go overseas, its nice to have a language that you can use with just your fellow countrymen (persons, whatever), that no one else can understand. Many other cultures can do that.
I personally don’t know any Maori (apart from the anthem and various words), and it’s unlikely I ever really will, but I'd like my kids to know it. And I'd like one day for NZ to embrace the two cultures as separate (so we don’t loose part of one to another), but both as heritage of every New Zealander, so we are basically one.