How would a prominent country go about changing its ccTLD in practice? (in particular, if New Zealand gets renamed to Aotearoa)

The Māori Party has recently started a petition to change the name of New Zealand to Aotearoa by 2026. Like all country name changes, this would affect the ccTLD, but this one presents challenges due to its prominence. New Zealand's current ccTLD is .nz which has 724,001 registrations (for comparison, that's almost half of .jp). For the sake of discussion, I'll assume that the new ccTLD for Aotearoa would be .aa (simply because .ao, .at, .ae and .ar are already taken).

I have a cursory awareness of previous ccTLD changes but those were in very small places or happened many years ago, so the number of domains and web users were much fewer. New Zealand changing from .nz to .aa would present a problem of scale as it's possibly orders of magnitude more than any ccTLD change previously attempted. It's the scale I'm mainly asking about. I'm curious if there has been any prior consideration or preparation for of this level of change.

1. Who leads the change? Does the country's government request the ccTLD change and schedule, or do ISO and ICANN just decide the new code and impose it?
2. Are we technically restricted to the "usual" way of transition? From my understanding, it would look like this:
   • ICANN creates a new .aa entry and puts it in the DNS servers, which creates the new domain.
   • All .nz registrants get notified of the transition and its deadline. They have to re-register every single address under the new .aa domain, with some co-ordination to avoid conflict and squatting. They also have to each implement their own redirection to point their users from the old .nz addresses to the new .aa addresses during the transition.
   • Every hyperlink, bookmark and API call with .nz has to be updated to .aa.
   • A public service campaign gets all web users in the country into the habit of looking up .aa addresses instead of .nz.
   • Once the transition period ends, ICANN deletes the .nz entry from the DNS servers, which wipes out every .nz address from existence. If anyone missed the transition deadline, they're out of luck. Any web resource that didn't get moved to .aa is no longer accessible. Any hyperlink, bookmark, API call or web user trying to access a .nz address is now faced with a 404.
   • This process was probably manageable for cases like the Congo in 1997, but it sounds hideously disruptive for Aotearoa in 2026.
3. Or are there easier ways to go about it? For example, could the powers-that-be simply assume that there will be a one-to-one mapping between the old .nz addresses and the new .aa addresses and simply duplicate all the address registrations to the new domain in one go? Could the address redirection from .nz to .aa be done automatically by the DNS servers for the transition period? Things like that.

This question was inspired by New Zealand but it also applies generally. Is there any existing plan to manage ccTLD changes where prominence or scale would pose a practical issue? Are there any technical shortcuts to ease the transition?

[this question was cross-posted from Software Engineering Stack Exchange because I was advised to put it here instead]

Country code top level domains are delegated by IANA to some managing entity. With a new ISO 3166-1 alpha-2 code, a legitimate claim, and evidence of competently running a DNS server, a new delegation could be made to start a new one. Probably to the same manager of the old name, but that is not a sure thing. Delegation being the key word, because IANA does not control what managers do with their zones, only what is in the DNS root.

.nz currently is administered by InternetNZ. Their activity report shows them tracking just under 725,000 names. But no mention of tracking a new TLD in their planning. Whether it has yet to come to their attention, or a new entity will manage Aotearoa's TLD, or this won't actually end up happening, I don't know.

Timing and nature of the transition isn't really a technical question. If the government says .aa is open for business and .nz will someday be deleted, better plan for that when securing domain names.

Doing DNS magic at the ccTLD level has its limits. Granting the existing domain customer example.aa may save the trouble of registering it. However, your zones and TLS certificates all are example.nz.

Some interesting precedents. .zr was deleted in 2001 some years after the Democratic Republic of the Congo was renamed. In contrast, .su outlives the fall of the Union of Soviet Socialist Republics.