I have an interesting idea. A lot of these consumer grade CPEs haven't sufficient ROM/RAM to do dual stack. So, throw out the IPv4 stack altogether. Get rid of the nat, port mapping, all the crappy broken SIP ALGs etc, everything required to make room.
Leave only IPv6, with stateful firewall. Then, have the ISP do some magic* to make IPv4 visible. * I'll leave it as an exercise to those more sober and less tired to solve that problem. But I guess it'd mean some clever DNS capture/re-map for all locations which don't have AAAA addresses, remap them to a local 6 to 4 "proxy". how hard can it be :-D
