Really it should operate the same way that voting in France does. If I move to France and live there for 10 years, do I get to vote in elections? Do New Caledonians? I honestly don’t know 100%, but it looks like you have to live in France for 5 years and then apply for citizenship in order to vote (or be born in France, or marry someone who is a citizen, etc.) So, it seems like they should apply the same rules to New Caledonia. If New Caledonia doesn’t want you as a citizen, then you don’t get to vote. Living in another country for 10 years and suddenly being granted the opportunity to change national politics seems like an easy way for an Oligarchy to get started. A bunch of rich people buy apartments on the island, and boom, 10 years later they control the politics of the island. Again, I don’t truly know the ins and outs of the system, and I could be completely wrong, so if there is something I’m missing, please, let me know.
Edit: or just downvote without explanation. You know, whatever works.