The answer is a surprising: No - well 12 out of 13 maps pose no problems, but the 13th does; But as I had posed the question it's technically a yes.
First of all: I had seen he question JMoravitz refers to in a comment, but that only confirmed my suspicion that the pieces from the anniversary editions are a bit too large.
I just went through all the expansions and none required any thing besides up to 45 (some only 40 and some only 35) train pieces in each colour and 110 train cards (a few contained replacements for those), and both the Märklin and Germany editions contain that - but there is a problem:
The "old west" map is playable by up to 6 players and for that it contains white train pieces, which don't conflict with the red+yellow+purple+blue+green pieces of USA or Europe, but both Märklin and Germany contains pieces in red+yellow+purple-black+white. So if I only kept those, I wouldn't have train pieces in 6 different colours to play the "old west" map with 6 people.
I could probably switch the white pieces in "Germany" ("Märklin" also contain scoring markers with a different design) for the blue/green pieces in USA/Europe. I'll probably have to go through all the expansions again (and more closely) to see if that will cause any problems.