There's a company that operates a route between Chicago and New Orleans with a restored Pullman, attached behind a standard Amtrak car. See:

https://www.nytimes.com/2014/05/18/travel/all-aboard-for-a-t... https://railsnw.com/tours/Pullman/Rail-only-information3.htm

The economics of it are likely difficult, but there's at least precedent.