So, I had some time to think and check maps and compare with the curves! magazine...
a central-Switzerland tour could be something like this:
1. Start in Davos (all together about 250 km, without detour)
- Fluela Pass towards St. Moritz
- Albula Pass starting from St. Moritz, going towards Alvaneu (possbile detour: Bernina Pass with Glacier)
- From there go to Julierpass and head back to engadin
- in Engadin, the short Maloja Pass
- then back over Splügggenpass, with stay in Thusis maybe?
2. from Thusis towards central Switzerland (Ending after Klausenpass this is about 400 km)
- Laax/Flims towards Dissentis, from there over the Lukmanier Pass
- From there back to Switzerland over the San Gottardo Pass
- Furka Pass with Rhone Glacier
- Grimselpass
- On Grimselpass - the Panoramastreet Oberaar
- now down Grimselpass and then the amazing Sustenpass
- Klausenpass as finisher
Instead of Sustenpass/Klausenpass, it's possible to turn back after Sustenpass towards Andermaat and have a look at the already mentioned devils bridge.
Or Sustenpass back towards Interlaken/Eiger
Or Sustenpass/Andermatt and again Furka/Grimselpass and south towadrs Jungfrau/Aletsch Glacier.
I'll check also those passes except San Gottardo / Lukmanier in the next two weeks starting from Saturday, so after then I can provide a real experience and pictures.
I also don't know how many kms it's fun to drive and when it gets tedious. How many kms did you drive per day on your last tours?