It would be nice if one of the cruise ship companies that runs cars on the Alaska railroad during the summer or the Canadian company that runs its own trains out of Vancouver could get all the IP big domes and maybe some other surplus IP cars to run a daily summer time premium service on the Coast Starlight between Oakland and LA and/or the Zephyr between Emeryville and Reno. They might run it tri-weekly in the off season.
There are obviously a lot of wealthy people in LA and the Bay Area who could afford it. Cruise companies that dock in LA and SF could offer it as a shore package with deluxe hotels and airfare to and from their hometowns to attract wealthy people from all over the world who visit California.
I believe it would have to be a firm with big bucks that is prepared to offer good wages to attract the best people and make sure they can keep the cars properly maintained. They'd have to be prepared to lose money for awhile but the Alaska and Canada companies have shown that if it's properly promoted and offers a high quality service it can attract enough passengers to make it profitable.
They might have to try and offer some incentive to UP to make sure the trains run on time so they don't end up making refunds if the train is several hours late.
I don't know if premium overnight Pullman service could succeed on the Starlight or anywhere else but daytime travel has a good chance if done right.