True, dial up users do get a new ip address daily, but how many dialup users are there out there?
Don't know how this is handled in other parts of the world - here in Europe most people get a new IP every day. A connection is interrupted by providers at least once a day. Even DSL-users online round around the clock are called "Dial-Up users". So we're talking about 100 million dial-up users alone in Europe, I guess.
The "second thier" model is a nice one, IMHO. Didn't say anything other. How to implement something like this should be discussed in details from persons directly involved and with enough background knowledge.