I understand why Seattle is so tough, but KSEA and KPDX will always be my dream ticket to fill the gap in the West coast with quality add-ons already at KSAN, KLAX, KSFO and CYVR with PANC and PHNL to boot.
In complete agreement with you, I like to purchase scenery that is with in flying reach of other airports. KSEA would be another stop on the west coast indeed, but it hardly fills a gap since it is very close to CYVR and about 583nm from KSFO (used the measure tape in google earth lol). But I like that it gives you another flight destination option on the west coast, that is why I am with you.
KIAH would only compliment KDFW as its closest neighbor and the next available scenery to fly into would be KORD or KATL about 586nm -868nm away and from there isnt much of a cluster of other airports to do regional flights to. Just Tampa and Washington area. Not much fun there! When I make a decision to purchase a new scenery before I click on "Submit" I use Google Earth to see where can I fly to from the scenery and if it is an isolated geographic area with neighbors, that kinda turns me away from saying "YES" as in the case of Vancouver CYVR lovely scenery but I just dont have airport options to enhance the fun! Sorry FSDT but I went with Fly Tampa Montreal which is closer to KBUF, KBOS and freeware CYQB! CYVR to PANC or KSFO would be a long and boring flight. Once that west coast gap starts to fill in with more destinations is when I will look at CYVR!