Has anybody looked at the practicality of installing modem pools in each
telco switch location to grab the dialup user's traffic at the IP level
and then route it to their ISP of choice for authentication and further
routing. In other words, an ISP wouldn't buy phone lines, modems and
terminal servers, they would buy IP access ports.
Southwestern Bell has described such a service they claim to offer here in
Texas, though I have not seen it yet. At one point, I had heard that
Ameritech and PAC*BELL were bothing looking at something like this. I never
saw if they actually did it or not, though.
CampusMCI is something like this, but of course there is only one ISP
of choice in that case :-).