I came across that 121 single DMU aka the bubble-car. Funny name eh? and I though ah yes, I drove the BR 101 and loved it. But that 121 could do with some activity. Originally in TS 2022 it's placed on the GWR line among the modern trains. I assume this would be the case here two? First and for-most would like to see that 121 again?
The Class 121 worked alongside the Class 117 sets until 1992 on the Paddington local services at which point they were replaced by Class 165 (initially /0 before handover to Chiltern Line with 75mph top speed followed by /1 Thames Line variants with 90mph top speed) and later Class 166 units from 1993. A very good suggestion though.
Not another thread where we are splitting hairs about what BR means. Why even bring German stuff into a thread which is emphatically about a UK traction type, in this case a single car DMU?
The Class 121 from TSC comes in Network SouthEast livery for use on the old Great Western Main Line route that also included NSE-era stock in the european loco and asset pack the route has as a dependency, which are used in the included scenarios. For authenticity the Class 121 wouldn't be seen in real life operating alongside GWR livery trains on the Paddington to Reading segment, and any representation of this in TSW would be best coming with some extra NSE-era stock, probably a new separate timetable, and possibly even an era-modified route (which I don't see happening). A better alternative would be to have the similar Class 122 on West Cornwall Local in Regional Railways livery.