As it happens, the Germans did plan to build a 2-6-8-0 Mallet. This was to have been built by Borsig of Berlin, and would have been the DRG's class 53⁰.
There is conflicting information as to whether construction ever went ahead; a couple of sources claim Borsig got as far as building the bare frames.
Whatever the truth of the matter, Märklin produced a model of the Class 53 in the 1970s, and continued producing it, on and off, over the following decades. It's quite a sight.