From your descriptions of your "routine", I have to say that I cannot understand it. Your descriptions of dial-up also confound me (I'm on a T3 9 hours a day and can't stand dial-up at home). However, to each his own, I guess. It is discouraging, though, that some minor feature changes in an otherwise very much improved OS were met with such a flame (with top billing on oreillynet) simply because they broke your extremely fragile routine.
Ok. So there's my flame back. I really think you are looking in the wrong place here. The OSX dial-up infrastructure is really just our friend pppd and related programs. From what I remember, Apple patched pppd to accept an extra parameter which allows a user-defined plugin to be loaded for event notification. The Apple connect scripts pass in a system-defined plugin that makes sure the UI is always in sync (ie. displaying in the menu bar, keeping network preferences "live", etc). You can inspect these options by reading the pppd man page closely or passing the correct options to "ps" to get a look at what the Apple connect scripts are doing.
I suggest that you look past the Apple GUI scripting you are doing and seek a more "Unixy" solution. I solved this exact same problem on Linux 4 years ago using a combination of pppd, diald and chat. It was a bit of a pain back then, but I know that things are somewhat easier now, especially if you can forgo the "automatic connection" and just force a connection manually, this is practically just a couple lines of script. Still I know that tautomatic connection is possible from a pure unix tools aproach (in fact I wouldn't be surprised if this is exactly how Apple implements it under the covers).