Jeff, I was going to suggest something similar, but was beaten to the punch.
I'm surprised that you, in all your infinite geek-wisdom, haven't come up with a solution yet.
Time for you to invent the XTB-DVR
Seriously. I don't know anything about the Panasonic DVR, but perhaps there is a way to make a user-friendly interface for a device to change the channel on the cable box at the appropriate time.
Years ago I had this in NY, with Time Warner cable. They offered a "Watch 'n Record" box, which had two tuners in it. It had connections to feed out to the VCR, and another to feed back in FROM the VCR. It had a separate feed out for the TV.
To record stuff, I would first set it up on the cable box, and then set the VCR to record on channel 3 at the appropriate times.
It sounds like this is about the same as what you are facing with a programmable "channel changer"
It may take a little practice, but this would probably be a lot cheaper than getting a Tivo, or a DVR from the cable company.
I don't know what the controls on your DVR are like, but maybe there is a way to skip the DVR programming altogether, and have the "channel changer" turn it on to record "live" when it changes the channels on the cable box. Then, there is only one device to program (the "channel changer").
Another way to go would be to build your own PC-based DVR, with a digital tuner card in it. It might be cheaper than getting two TiVos, but still not cheap.