SEA was never a large base. I was based there on the guppy and the 777. It was always one of our smallest. The 777 had 1 flight a day to NRT, which never justified the base. I flew with a member of the MEC based there who bragged about how they pulled off the 777 base is SEA.

A VB might work for DAL as they are structured differently. They have one gigantic pilot domicile less than an hours flight to most cities in FL. They have very frequent service to a lot of those cities. I can't think of a base/VB city that matches that with UAL. LAS maybe. But SFO and LAX combined aren't as big as DAL's pilot domicile in ATL.