No idea, but people do it. Every time this comes up on HN there are dozens of comments about how they like hiding their devices behind a NAT, for security
"I have a device acting as both a NAT and a stateful firewall, why are you making me switch to IPv6 and in the process drop both the NAT and the stateful firewall?" is a non sequitur.
What I'm saying is this: There exist people in the hobbyist space who believe that when their devices only have private IPv4 addresses such as 192.168.0.0/16 that this meaningfully increases their network security, and that if their raspberry pi has a globally-routable v6 address that this weakens their network security, even though this is bogus because NAT is orthogonal to network security considerations, and that this belief contributes to IPv6 hesitancy.
We desperately need a standardized protocol to look up addresses via names. Something hierarchical, maybe.
> with v6 you can't rely on NAT as an ersatz firewall
Why would you not just use a regular firewall? Any device that is able to act as a NAT could act as a firewall, with less complexity at that.