You mean Spokane-Portland-Seattle? That would be tough since it would require a backup move at PDX and would be right around the 7 hour mark, so longer.
When the Railpax plan was being proposed, all of the passenger service in Oregon was proposed to be discontinued. Portland had four east-west trains in 1970. The Oregon PUC proposed that the northern transcontinental run via Vancouver, Washington with a bus connection to Portland. An alternative was to run on the UP between (Pasco) Villard Junction and Portland. Either alternative would have added time, but so did running via Grand Forks rather than the cut-off.
As I've reported before, heavy-duty politics were involved. One of the Amtrak board members was the former Republican congresswoman from Yakima. Washington's two Democratic (majority) very senior senators had more influence than Oregon's very junior Republican (minority) senators. An
Oregonian reporter was coincidentally in the room when Senator Warren Magnuson, long-time member of the Commerce committee, took a call from the former congresswoman clearing the route selection with him.
In 1973 a daylight train between Seattle and Spokane was proposed for the fair in the latter city. Oregon DOT suggested that by interlining it with one of the Seattle-Portland trains and running it on the UP to Spokane it would only require one set of equipment and it would have connected in both directions with Trains 11/14. Instead, at Senator Magnuson's request it ran over Stevens Pass, requiring two sets of equipment and overnights in Seattle for California tourism. A Spokane-Portland train did run weekly during the fair - a UP special for VIP's only.
The Yakima route was particularly obnoxious to Oregonians because of spending all day riding around Washington state and then getting back to the Columbia again at Pasco, which had formerly been a four-hour ride. Therefore, I worked out proposals for ODOT to Amtrak for a Portland<>Pasco section of the
Empire Builder running on the UP
. This didn't get much traction till the closure of Stampede Pass loomed and then a Spokane - Portland train with California connections eased the relocation of Trains 7/8 to Stevens Pass. The BN North Bank line would have worked better with the Los Angeles<>Chicago through sleeper switched in Portland, but that last piece never came about, likely due to delays on Train 14.