I must admit that I'm still struggling to understand the use case.
so allowing consumers to *spend* using BTC would just require an issuer to support it and, perhaps for teh Visa/MC network to add support.
My suggestion is that getting an issuer (like Visa/MC) to accept BTC as a currency is a monumental task that won't happen soon. And that solution centralizes the otherwise decentralized Bitcoin economy by funneling through the issuer (who can make whatever claims it wants to break down anonymity if you want to use that service). Which is why I'm searching for another solution.