I suggest a Southern Pacific Coast Railroad That runs from Santa Cruz to Oakland in 1939. The rail ended in 1940 due to mudslides and wash-outs. There were 8 tunnels running through the Santa Cruz moutains. One Summit tunnel at Wright Station been dynamited in 1942 due to WW2. After the war, it resumed in 1947 through 1959 where the Daylight train been running.
SP in the 50s would be awesome. We need SP FM Trainmasters, EMD SD7/9s, or Alco RSD-15s for heavy freight, GP7/9s, EMD SW or NW switchers, or Alco S2/S4 switchers, and the Daylight with Alco PA-1s, EMD E7s, or EMD F7s. Maybe we could get the GS4 4-8-4s.
If it's during the 40s and 50s we should also get some more steam, like the MT-4 mountain types, P-8 Pacifics, maybe even a GS-2 or GS-3, and an 0-6-0 for yard duties.
I would love to have this route in TSW or TS2020 it woule be challenging and fun to have using steam or diesle would make it a blast. i hope this route becomes a reality the most.