[welterde]

> No, and this is a good thing, only IPv6 devices which have their own IPv4 address/network can issue IPv6 addresses on that network.

So you will still need tunneling to make it work. As you will still have to run CGN to get all your customers online. Unless of course you do want to change the network infrastructure. At which point your solution gets much worse than plain and simple IPv6.

> It keep being phrased as "what is the source address of an IPv6 host on an IPv4 network". It seems to me the answer should simply be "the first 32 bits of the IPv6 address" - and it seems stupid it's not structured like this.

Sure.. that solves the routing problem (except for IPv4 routing table explosion), but doesn't solve the problem that IPv4-only hosts still can't talk to IPv5-hosts. You send [IPv4][IPv5] packet to IPv4 host. Huh? What's that IPv5 thing? Or the other way around.. IPv4 host sees AAA record (with IPv5) in DNS..

Your proposal solves nothing that can't also be done with IPv6 and tunnels if you are really keen on keeping your 5 old router running a few more months before throwing it away (which you can't do anyway, as your limited FIB size will force you to buy new hardware anyway, due to IPv4 route table fragmentation).