Though I totally respect the advice of limiting countries to reduce stress, the whole point of this specific trip is to do a country hopping, backpacking sort of look. Now I'm not going to 10+ countries... but I'm still seeing a handful. I had 10 additional days to play with what I already had with Europe, and it gives me a total of 40 nights. This will probably have to be further down the road til covid restrictions are more lenient. But the idea is 5 nights in London, 5 nights in Paris, 12 nights thoughtout Italy, 7 nights in Greece at the tail end of the trip, which leaves me 11 days to do Germany + Austria, or Germany + Switzerland.
Trying to include Berlin and Vienna might be a little out of the way, so I can totally see an argument for Germany + Switzerland where i skip Berlin and go through the western/southern part of Germany and down towards Switzerland and Italy. If I did this method, I would still want to see Munich so I see at least one of my intended cities. It might also be easier since I really only need 3 or 4 nights in Switzerland to take a brief break and do some fun, no stress hiking.
If I kept to the original route, how could i make all of those cities work with 11 days? Prague & Cologne both sound super appealing, but I feel like anything LESS than 3 nights (2 full days after you consider the travel day) in a city would almost seemed too rushed, even for this sort of trip.
