So, those mythical IPv6-only internet users actually exist :) That's some great network engineering.
I once needed something like that for the perhaps more common inverse purpose, to work on something IPv6 from within my happy IPv4-only connection. A more limited, but quicker solution given full control of a server - I set up a SOCKS5 proxy, using:
ssh -D 1080 -N myserver
and set my browser to use it. I think that it could also be set system-wide, but wonder if that might break the original ssh connection, holding it all up :)