Itinerary Advice--Italy, Switzerland, Germany

Hi,
I like the outline of the trip; it already works well as it stands except days 18-19. I would suggest the following optimizations:
- Florence-Bologna-5 Terre makes you zigzag a lot; Bologna's nice enough but I would skip it, and spend 2 nights in 5 Terre
- If you're really keen on Bologna, with 5 nights in Florence you can day trip there from Florence. The trains run late (10 PM), you can even have dinner in Bologna
- Are you interested in visiting the Rhine Gorge between Mainz and Koblenz? I think it's worth it, when you're in the area. You could stay in Mainz for 2 nights, day trip to the Gorge, and go directly to Frankfurt aiport from Mainz. You need an extra night, which you can take from Bologna if you follow the above
- I like Milan enough to spend two nights there, yes! It is a pleasant city for a day or two, with a handful of great sights.
- However I would skip Lugano. Quite similar to Como, but less pretty in my opinion, and with Swiss prices. You can easily do the Bellaggio-Luzern trip via the same train route as Gotthard Panorama in a day from Bellaggio. You go from Bellaggio to Como via bus or boat, then train to Bellinzona, another train to Erstfeld going through Göschenen, and a last train to Luzern. Exact route may vary: use the SBB journey planner and look for Como to Luzern via Göschenen.
I think that the boat leg of the "official" Gotthard Panorama Express is a bit long at 2.5 hours, so I'd consider staying on the train instead. You'll be able to take the boat on a day trip to Mount Rigi from Luzern

So much great advice here. It will take me a little while to absorb all of it but I think this will be extremely helpful information for us. We were in the Rhine Valley 2 years ago. Left Amsterdam via train to St. Goar where we did a few hours boat trip on the Rhine and came back via train to spend the night in St. Goar, then on to Rothenburg ob ter Tauber for a night and on to Nuremberg. Not sure if the Rhine Gorge would be similar to what we have already seen?

By "Rhine Gorge" I am referring to the same place as where you went! So I guess you could spend more time in Switzerland instead. The Bernese Oberland area comes to mind, or you could bring back Lugano or Locarno to the game.

Obviously you had no way to know that we had been in the Rhine Valley. It was a great suggestion--a place we would enjoy going back to but prefer to see more amazing places that are new to us.

Would you recommend Bernese Oberland over Bern? How would be the best way to fit that into the logistics of our trip?

More Questions: We are not planning to travel until late April 2020 but I am putting in random dates for this fall to see if I can understand the train option from Como to Luzern that you suggest. I keep getting stuck and encounter a message that I cannot book that entire trip.

We were planning to stay in Lugano because it was our understanding that the GPE started there. We were hesitant about not staying there and possibly missing the train for some reason.

Am I correct that the train route you suggest would be less scenic and lack the dome type cars that we would find on the GPE? Is the route you suggest--less expensive but less scenic and the train not as nice? Or am I misunderstanding something here.

I have tried looking at the SBB site but when I put in the suggested trip Como to Luzern via Goschenen and click on the details, I am unable to see any routings that include Goschenen. Does that make sense? Even though I am requesting that it be included, will it now show up on the itinerary?

Personally I would take a day from Orvieto or Assisi and add a day to Cinque Terre (if you are planning the hike that a full day). Assisi can easily be done in a FULL day. We are Catholic so it was a high priority and we still felt good about the 1 day there. But Cinque Terre we did three nights and could have stayed forever! Its amazing after all the day trippers leave and something unique and lovely.