Tosh,
It's going to be hard to top the location that Peter and Cees found for us last year. But the Mosel would be one to consider. A couple of years ago, BK and I attended the auto show in Essen, drove south to the Nurburgring where I ran a few laps, and then continued through the Mosel and on to Stuttgart. Along the way we spent a night in Beilstein and diverted to have lunch in Luxembourg just to say we had. The Mosel is a lovely drive with a few interesting little side roads. Would Trier be a good place to consider visiting on a Mosel Valley weekend?