It's not like they don't have an historical reference to follow.In my opinion, it would be best to reinstate the Pioneer and the Desert Wind. The cities served by these trains have gotten a lot bigger since they were discontinued.
The Pioneer would be a section of the Zephyr, and would leave Denver to serve Cheyenne, Boise, Portland, and Seattle.
The Desert Wind would also be a section of the Zephyr, and would leave Salt Lake City to serve Las Vegas and Los Angeles.
I know places like Columbus, OH, rank high on the list of large cities not served by Amtrak, but wonder where Metropolitan Las Vegas is on that list.