There is consensus that Seattle needs a first class lounge. A transfer point between trains, a major city on a corridor with business class, the origin point of two trains with sleepers, a transfer point from other one-a-day forms of transportation (ships and ferry)... and the waiting room is small and hard-benched without easy access to food.
(By contrast, Denver's main waiting room is so nice I doubt anyone would go to a first-class lounge unless it was full.)
Emeryville and Sacramento are other candidates for first-class lounges, as are Tampa, Miami (which station, though?), Orlando (which station, though?), Charlotte (new station), Raleigh, and Richmond. But Seattle seems like the station with the most overspecified reasons why it needs one.