Actually I would be happy enough if the German track was included AT ALL, so no need to add it to the menu (and just be selectable via the audio button on the remote). Of course, adding menu entries, separate German Greedo/Jabba-subtitles or even multi-angle crawls would be the icing on the cake.

I've authored quite a lot of DVDs (albeit no multi-angle yet), but I haven't dipped my toes into Blu-ray authoring (or Java-scripting, which is used for Blu-ray menus, as I understand it). Otherwise I would just give it a shot myself. Of course dark_jedi's Blu-ray set would be the perfect starting point for adding anything more.