I know Dovetail isn't doing US freight routes right now or have access to certain licensing . But if things change, the best route in my opinion, is the CSX Richmond, Fredericksburg and Potomac subdivision. The route runs 177 Kilometers(or 109 Miles) from Washington DC to Richmond VA. This route is not only a major freight route but also a great passenger route. In addition to 20 daily freights, there are also around 20 Amtrak trains daily and north of Fredericksburg Virginia, 16 Virginia Railway express trains daily. The route should run from Washington DC union station/CSX Benning Yard to Richmond VA Main street station. Rolling Stock MPI MP36PH-3C CSX ES44AH Amtrak P42DC Not to mention the Amtrak Auto Train runs this route south of Lorton, Virginia. Have that included would be great. A period route set in the early 1980s featuring the massive Potomac railyard would be cool too.
The RF&P ES44AH CSX Heritage Unit would be cool to see, along with the rest of the CSX Heritage Fleet. I'd love to finally have Amtrak power (with a Siemens ALC-42 Charger or P42DC Genesis). A CSX 3GS-21B Genset, ET44AH, SD40-3, GP40-3, GP38-3, SD70AC, ST70AH, C60AC, C44-8W, C40-8/C40-8W, and/or SD23T4 would be great to see in game. The VRE MP36 has a nice paint scheme, and should also be included.
One locomotive on your list is already in TSW C40-8W. Hopefully if this route is made they have services with locomotives from Sandpatch Grade.