The Uerdingen railbus (German: Uerdinger Schienenbus) is the common term for the multiple units which were developed by the German firm of Waggonfabrik Uerdingen for the Deutsche Bundesbahn and private railways after the Second World War. These vehicles were diesel-powered, twin-axle railbuses of light construction. The diesel motors were built into the chassis underneath the vehicle. The VT 95 (later DB Class 795) and VT 98 (later DB Class 798) of the former Deutsche Bundesbahn in particular, are associated with this concept.
Together in a pack with a Köf on a historical german route (we have none of those yet, but I did suggest two '90s routes if you're interested, The Saalebahn and the Main-Weser-Bahn) this could be great. It would be a 'lightweight' pack or something like that. However, we need a historical route (or a heritage railway) that fits these units first, and even the two I linked wouldn't really fit the railbusses.
What about Frankfurt City Link Line?It has cargo services and passenger services operate by Historic Railway, Frankfurt .And it can also has tram experience.
And there's another same route called Städtische Verbindungsbahn Frankfurt am Main Here's the link https://de.m.wikipedia.org/wiki/Städtische_Verbindungsbahn_Frankfurt_am_Main It seems more funny Video link
Another great spot where the railbusses were driving around until the 1990s is the Westerwald area between Au (Sieg), Altenkirchen, Montabaur and Limburg. They could even be combined with ETA 150 accumulator units and maybe V 100 (BR 212) light cargo services. https://en.wikipedia.org/wiki/Limburg–Altenkirchen_railway https://en.wikipedia.org/wiki/Engers–Au_railway
Definitely a loco downloadable content because it can be used on RRO HMA SKA RSN Main Spessart Bahn and HRR as Legends of the Deutsche Bundesbahn since those routes might have diesel only sections