Seattle would make a great central city for a PNW region, with its unique geography, water access, and culturally-distinct districts (Fremont, SoDo, U-District, Belltown, Ballard, etc.). It also has a reputation as a home for coffee lovers, and the cafe mechanic of Kalos could easily be implemented here.
Also, lots of the surrounding land is ripe for cool routes: the always-visible Mt. Rainier and the Cascades have tons of potential for exploration; the eastern half of the state can support pokemon that prefer drier climes in the brushy, hot, and dry Columbia Plateau region; and the San Juan Islands are a late-or-post game spot with some rare and unique pokemon on the smaller and more difficult to reach islands (Friday Harbor would also make a great pokemon town). As a post-game area with lots of tough pokemon and large dungeons (a la Mt Silver, but bigger), the Olympic Peninsula is a largely untamed rainforest and mountain range mostly inaccessible to the general populace - no roads lead directly through it, only around (look at a map of Olympic National Park). With some small towns around the peninsula (Port Angeles, Forks, etc.), I feel like it has high potential for long endgame excursions.
