I like the idea of Cajon Pass and Tehachapi Pass combined as one route, but not as separate routes, so I think this can be a good one.
Amtrak's Southwest Chief runs over Cajon Pass so there would be passenger opportunities on this route
But I must say, I doubt that Dovetail Games would make this anytime soon due to the BNSF licensing issue. However, it seems more likely that a third party would tackle Cajon Pass or Tehachapi Pass (or both) for Train Sim World at the time of this licensing issue.