Anyone have any speculation on how a 73 base in Seattle will effect movement westward?
Yes, positively!
Longer answer: There are a lot of fairly senior FO's on both the A330 and 75/767 based in Seattle that will try and bid captain on it. And I won't leave out SLC and LAX guys either. For that matter, I'm sure there are guide a few guys that commute out of Seattle to the 737 in both LAX and SLC. Establishing any base out west will have a positive effect.
Denny