If you're adding anyone at all (and they should jettison teams, not add), I'd be fine with Oregon and Washington. Each has something to offer from a football front and passable history in basketball.
Cal and Stanford should probably go the WAC, or Big XXIV if it will take them. OrSU and WSU are in the same boat, though probably more attractive to to the Big XXIV.
The issue with all of this is that it creates a product that appeal to a broad "college football fan" while ignoring that the sport lives and dies with team-specific fans. And to maintain your proper volume of happy and therefore donating fans, bodybag games have a crucial value. It's like expanding the old SEC West problem.