[paperplatter]

But you're still using ipv4, which cannot be upgraded in-place the way I described. I responded to a sibling comment about the second question.

[kemotep]

What makes the 4 to 5 NAT different than the current 4 to 6 NAT and DNS?

[paperplatter]

4-to-5 NAT would be effectively the same if that's what you use, but I don't see why you'd need one.