I know hydraulic brakes, Maguras in particular, are hugely popular in Germany for trekking bikes, but for a coupled bike I'd seriously consider changing out to standard V-brakes. I don't think you'll notice much (or any) loss in stopping power, and it will make things WAY easier when packing.

If you don't yet have S&S cases, then it's up to you whether you want to go to the hassle of breaking the bike in two vs. using a bike box. (How much does the airline charge for a bike in a regular bike box, and are you willing to pay it?) In the past I've made two S&S sized-cases (26x26x10 inches) out of cardboard bike boxes and used them as disposables. They worked pretty well, but took some time to make.

BTW, I was in Mannheim/Ludwigshafen area back in June; did a short weekend bike tour up the Rhine from Mannheim to Koblenz when I was on a business trip to Walldorf. You have a lot of great riding areas around there!