I suggest the following route: the Southern Railway in Baden-Wuerttemberg from Ulm to Friedrichshafen or further to Lindau Reutin / Lindau Island. That would be the perfect addition to the Vorarlberg S-Bahn. Ulm as a city with the large cathedral and the river Danube, the route south through gentle valleys, past Ravensburg (city of towers) to Friedrichshafen Airport and Lake Constance. Many connections are also possible, e.g. RJX32, ICE 32, IRE 3, RE 5, RB 91, RB 93 as well as freight traffic.
