> 1) my stateful firewall is going to break most of that anyway

Your CPE is probably running UPnP IGD and/or PCP for hole punching of P2P services, and IGD/PCP can hole punch just as easily for IPv6.

> 2) if cg nat is as popular as people claim then they won’t be doing that as it’s not an edge case

It's not whether CG-NAT is an edge case or not, it's whether there are things that are completely impossible with it or not. Want to play with your friends on your Xbox/PS? Too bad, CG-NAT makes it completely impossible.

Why should we be happy with a technology that makes certain use cases impossible? On what planet is that a good thing?