I feel like the hard part there is actually accessing all the IPv4 systems to change how they handle addresses. I don't know the full scope of difference, but I

I feel like the hard part there is actually accessing all the IPv4 systems to change how they handle addresses. I don't know the full scope of difference, but I feel like once you can do a software update to all of your devices, the cost of increased complexity in protocol would be relatively constant between a minimal and actual v6. You are just pushing different data through the update.