I have been to those countries and you have a good list. Given you our flying into Frankfurt you must experience Germany, obviously. The rest of the countries you show I would prioritize like this: Switzerland, Italy, The Netherlands, Belgium, France. If it were me, I would spend all the time in Germany, Switzerland, and Italy. Those countries are beautiful, the people are great, great beer, great food (except for Germany), nice people, and unbelievable scenery. I could spend months in just those countries. But just about wherever you go it will be great. Have fun and I look forward to the pictures.
Note: Germany does have good food, I like it, but it isn't as well liked by the masses compared to the others. I have never heard anyone list Germany when they talk about the best food in Europe. Also, France may have the worst food, in my opinion. I usually lose a lot of weight when I go there.