If you're in southeast asia the calculus changes. But the cost benefit analysis really leans against annexing hostile locals these days unless it's some nationalist mythology like China and Taiwan. And if you're in southeast asia I'd say future heat waves and climate disasters means you'll be more likely heading north into China than them heading south.
If it's a soft ideological takeover you're envisioning then that's really the responsibility of the democratic society you live in. Democracy falls when people no longer believe in its ideas or that it is an effective way of governance.
As for new Zealand, remember that you always have massive leverage over China in the form of nationalizing their purchases. Don't let wealth from China be a crutch. Enjoy it but know how to live life without it if the price of wealth is too great.
Meanwhile latest census shows that the Northeastern China peoples are shifting to the South.
I also think the treatment of the Uyghurs is scary. That the control of media flowing into China is so controlled that the people are not free. The lack of democracy means there are not enough checks and balances to keep the people free. The way the one child policy has been enforced is not humane. The oppression of religion means people are not free.
I am not staying any country is perfect only that I would not like to live under that control. I also fear in my part of the world we could end up under their control in my lifetime.