IPv6 NAT is also useful because the /48 IP block I get from my ISP may change. I switched from DSL to Fiber and I got a different IPv6 block. But because if that, I also needed to update IPv6 addresses to my local DNS server (which needs to work across VLANs - so link-local address is not an option there). With NAT66 I could just assign a private address space to my LAN and have it only translate it externally to WAN.
I am a network engineer who understands what those acronyms mean, and what you're describing is an order of magnitude more complicated and more work for the average use case in a large corporate environment, a small business environment, or a home network environment.
This is not simply architecture astronomy, it's the equivalent of planning an expedition to a planet to plant a flag with a title granted by the "International Star Registry"
I genuinely have no idea what you are talking about. Having the router advertise two kinds of subnet (one local and one global) is no more complicated than setting up NAT66. It's actually likely easier because it's likely something that can just be enabled with a simple setting, if it's not enabled by default, while NAT66 will probably require more intricate configuration, if it's even possible at all.
Not sure what the second paragraph is supposed to mean.
