We have one trip promised to our daughter for her college graduation to Italy, but she will be back in school in August, so its possible that my wife and I will take another trip to Europe before we end up going to Italy with her, so here's my latest, changing by the day, thoughts about it. Of course no time frame yet, but duration maybe about 23-25 days.
Arrival in Zurich, and spend time in Zurich (1st full day there to get over jet lag, and I really like the ambience of Zurich, a nice way to start the trip). Then onto Lucerne and definitely a boat cruise along the Vierwaldstattersee. From there perhaps some higher mountain experience like in the Berner oberland. This may be unusual, but I actually really like the lower elevation lake areas, so a trip to Thun and checking out the Thunersee might also be on the cards. I also really want to see Bern and I think my wife would enjoy the city. As someone who loves smaller cities, and a student of Swiss politics and its unique features, got to check out Bern.
Not sure how many days would be involved so far, but that would give us a nice taste of Switzerland before heading for Germany.
First stop in Germany would be Freiburg, where I spent a semester auditing history courses way back in the late 1980's. This time I want to see alot of areas that I foolishly missed seeing back then, such as some of the black forest areas, so perhaps we stay a few days in Freiburg. From there I'm thinking about a stay over in Strassbourg, for a little taste of France and Alsace. After that back to Germany for some beautiful architecture. For sure Heidelberg and Wiesbaden, because those cities look beautiful. Also thinking about Mainz, Speyer, Frankfurt. Would probably want to do either a Rhine or Mosel cruise as well. Bonn might be as far north as we would go, and I want to see Bonn for its West Germany History museum, plus Bonn looks to have some nice architectural neighborhoods as well, such as Bad Godesberg.
We could fly home from Frankfurt, so might spend the last few days in the area, perhaps with a day trip to Wurzburg thrown in, with some time in Frankfurt as well. What I'd like to see would be a nice mixture of beautiful smaller cities, nature in different forms like nice lakes, rivers, forests, mountains, and if we end up seeing three countries as part of this trip so much the better. I think my wife would appreciate the variety of experiences as would I. Have to see what this itinerary ends up looking like but this is a very rough sketch. Also, I do like the open jaw aspect of it.