I think a nice addition to the UP Fleet would be the classic and legendary Streamliners. The Streamliners include The City Of San Francisco, The City Of Los Angeles, The City Of Portland, and a few others. The City Of San Francisco and The City Of Los Angeles traveled over the Sherman Hill as well as the Wasatch Grade and could travel up to 90 MPH! They were often hauled by EMD E6's, EMD E7's, EMD E8's, and EMD E9's. I think the UP Streamliners would be an excellent addition for the Sherman Hill route, or perhaps the Wasatch Grade route. Or perhaps, it should be included with another route set in the Transition/Early Diesel Era.
The E7s/E8s/E9s are cool, but what about the M10000 and other early Streamliners? I'd love a CB&Q route with the Pioneer Zephyr.
I made a similar suggestion in the loco request part of the forum, but it would be nice to get a dedicated Union Pacific passenger DLC for Wasatch Grade or Sherman Hill, maybe having someone like DTM make it instead of Dovetail.
Those would definitely be an excellent addition to Train Simulator. But sadly, the CB&Q logos would have to be unbranded for international customers.