Having walked in other areas of Germany, and knowing the people a little through my daughter-in-law and her family, I would seriously doubt whether anything there would be as basic as the Scottish Bothy
Not that I have ANYTHING to say against those fine and spartan shelters or the MBA -
I finally chose to walk the first half of the Rheinsteig starting Wiesbaden and finishing in Filsen on the way to Bonn.
I'll write an account of it when I get a chance, but I solved the question of the huts. There are numerous shelters - usually open on at least one side - which aren't intended as overnight stops, but would keep the rain off if required. No facilities though and I suspect passing Germans would be unhappy at them being used for an overnight bivvy.