Too much hassle on PlayStation.
On Xbox, you just change the settings to New Zealand and you're good to go. WTF?
How to play GTA 6 ~18 hours early on PS5, on your own account:
1 - Make a New Zealand PSN account
2 - Go to Settings > Users and Accounts > Other > Console Sharing and Offline Play > Enable
3 - Buy a New Zealand Gift Card online
4 - Buy GTA 6 in the NZ account
5 - When GTA 6 comes out, download it from the NZ account then go to your own profile
6 - The game will be fully accessible on your own personal profile, no need to play on the New Zealand account anymore
7 - Enjoy! You’ll be able to play GTA 6 at New Zealand’s midnight, which could be up to 18 hours early if you’re in the USA or about ~10-14 hours in Europe