Well, it's simple, it's already in ts2021, and would have some good Scenery. It would be from L.A, to San diago. The route is 111 miles, and would be great for more ad-ons, such as Coaster, and Metrolink. Pacific surliner going from L.A to San Diago. Metrolink going to L.A to Oceanside. And Coaster going from Oceanside to San Diago. That's why I think the pacific surliner would make a great ad-on to TSW2.
Its not a good location, as the only traffic will be the Amtrak Surfliner Trains only. Since DTG cant use the Metrolink, Coaster, or BNSF branding, Surfliner will most likely only come if they focus on the route north of LA.
Pacific Surfliner was one of my favourite routes for Train Simulator. It's also fairly high speed for American standards :P And the scenery was diverse enough so you never got bored. Also plenty of stops along the way. I'm upvoting this one, I'd love to see the route in TSW. The trains look cool too :P