Now I have almost all aspects of my European trip nailed down.
My last missing hotel piece - three nights in Paris - was resolved, with a booking at a Best Western in the Marais district. My friend DiAnne Grieser of Seattle, a huge Francophile and a frequent Paris visitor, steered me toward the Marais, since it's still quite close to the Latin Quarter, and I am glad she did; the Marais has cheaper hotels that are just as charming and comfortable. Plus, I do think the Marais - between its elite past, its Jewish population, and its gay culture - will be quite interesting. Most importantly, it's close enough to Gare de l'Est and Gare du Nord that I won't have to lug my bags through the Metro, but far enough to be saner.
I also have two train legs: the first from Munich to Stuttgart for the car pickup, and the second from Stuttgart to Paris after the car dropoff. The second leg was booked on a dirt-cheap price (reservation fee included), and it will be a direct TGV run. The only downside will be late-night arrival in Paris, but on the other hand, I will not have to rush my way into Stuttgart that day, since I will need to drive in from Interlaken. Sure, past Zurich, it will be on the A81 Autobahn, the speed demon's dream, but traffic jams can, and will, often happen! The first leg does not offer early booking discount, and because trains are very plentiful on the leg, reserving a specific train will probably be more foolish, so I will wait until I actually need to leave Munich before buying the ticket.
Another open item is arranging for the dropoff/shipping of the Mercedes-Benz. I will have to visit the shipper's Stuttgart office immediately after taking possession of the car; the shipper requests that in the delivery package, plus I need to give a week's advance notice before dropoff anyway (at least I'll come back to Stuttgart for the dropoff).
All this means I have all flights and hotels, and some of the ground transportation figured out. I also have tentative ideas on which sights I want to tackle in each city. I'll need to keep some flexibility in my plans, however, to prevent my trip from being a mad rush to meet a timetable, a common problem in my past trips. And of course, within the first day or two of driving, I will need to also buy a safety vest and expressway toll stickers - requirements for driving in Austria and Switzerland.