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 sett

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.