Thanks for that. As a transition-to-IP6 technology that makes a lot of sense, but I think it required a lot of prerequisite technology and work (i.e. IP6 itself). The hack I described could have been implemented on top of existing IP4 codebases.
Lukewarm deployment incentives for ISPs, lack of pull from device/app makers, etc have been the main problems. Apps adapted to the NAT world quickly, users forgot what capabilities they lost and started to fall into the NAT = security cognitive trap.
It’s a chicken and egg problem. It would have been nice if everybody everywhere agreed to build and use an entirely new network at the same time, but that was never going to be practical.
The actual problem at hand was lack of address space, and I think this could have been addressed with a more viable upgrade path - turn every IP4 address into x number of addresses behind it, and allow retail ISPs to remain IP4 only.