My ISP will route as many /64s to me as I want (I think I get a /48 by default, I guess if I want more than 64k subnets I’d have to justify it)

So I don’t have the changing ip issue. I do however have an issue if I want to change ISP as it’s a whole mess of rules to update rather than a couple of dns entries and two dst nat rule (one per public IP)

I believe the idea in v6 if you have multiple prefixes on the same network - including a local fc00::/7 one for local services. Layers and layers of things to break.