We have CGNAT and NAT46 and NAT64 and all sorts of tunnels today. It doesn't take a lot of current experience to imagine how much a v6 dependent on v4 and tunne

We have CGNAT and NAT46 and NAT64 and all sorts of tunnels today. It doesn't take a lot of current experience to imagine how much a v6 dependent on v4 and tunneled through v4 solution feels bad for the edges. The problem with IPv6 deployment has never had anything to do with lack of tunnels, "temporary" or otherwise, we've had that technology all along. It does matter if the major interconnects upgrade. We've got decades of data now if you want to science it. In your scheme if you aren't mandating every v4 address be a NAT "forever", then you've at best got huge sections of "dark" addresses that can't properly be used without some traffic accidentally blackholed. If you do mandate it you run the risk of bad actors taking advantage of it and toll bridging the chokepoints at the tunnels. (Which is also in theory a massive man-in-middle security risk.) Either way you are locked into the whims of IPv4 address owners and the mistakes of past IPv4 allocations (including all the early /8s that went to big companies just because they asked the right year and the fact that the large continent of Africa has never had anywhere near enough address space, and a fraction in comparison to Europe and the Americas). I really don't see the economic incentives that would have made that addressing system better than the IPv6 we got, but I certainly see a lot of them that would have made things much worse.