I could see the moa being reintroduced to new Zealand's islands as they'd have the environment the moa enjoys and would not have predators that could eat them. I'd guess the reason why is the kings of aotearoa would want them as status symbols, and the island would act as a barrier against invasive species and poaching them.
The risk is actually people. Moas were quite vulnerable to human hunting, both of adults and eggs, and were slow-maturing (10 years to reach breeding age regardless of species). A destabilised political environment on Aotearoa doesn't help stop the hunting of them.
PS what European/American crops would enter aotearoa? Potatoes, oca and ullaco could be a boon to every farmer, and quinoa would be good too. Wheat should still be usable, and millet, buckwheat and rye would still be very useful for using marginal lands.
The thing about Māori farming ITTL is that it makes heavy use of a particular style of farming which isn't easily adaptable to European (or most American) crops. They use perennial tubers and perennial trees, with negligible plowing and a great deal of use of crops to replenish the soil. Switching to, say, wheat or quinoa is not just a matter of using a new crop, it's a matter of switching to a whole new style of farming. It doesn't necessarily go well together.
That doesn't mean that new crops won't be adapted, but the process will be slow. And only higher-yield crops (or ones which grow in areas unsuitable for the core crops) are likely to be chosen.
Wheat is potentially usable if farmers switch to wheat and wattle farming as a combination, less so if it means giving up wattles as well. Millet and rye don't yield all that well to matter over most of the country, though anything which can grow in the far south (farther south than about Oamaru) would be more attractive.
Potatoes do yield higher per acre than red yams, but aren't perennial, so the incentive to switch isn't quite the same. I'd expect them to make some inroads over time, but not as quickly. Oca and ullaco would probably be only minor crops, grown for flavour or in specialty uses but not staple crops.
I'd expect crops like onions and garlic (and maybe tomatoes, where suitable) to make significant inroads as flavouring crops rather than providing a significant proportion of total daily calories.