Seattle has dozens of online-only booksellers, businesses who keep large quantities of books onhand but sell primarily (or totally) through sites like AbeBooks. Some of these sellers used to be retail spaces. Some of them still maintain small retail spaces. What if these booksellers banded together in the Elliott Bay building, like the Fremont Antique Mall? Elliott Bay is taking their shelves with them, so the space would need to be re-imagined anyway.
If the space was filled with a collection of booths, each with their own specialties, it would be unlike anything else in Seattle. The sellers wouldn't rely solely on sales from the retail space (they'd of course make a lot of their business online still), but they'd draw a lot more foot traffic by banding together than they would in their own retail storefronts. Combined with a few other booksellers like Revolution Books, a handful of people in Seattle's craft community who work on book-minded projects, and maybe hosting readings, open mics, workshops, and things like that, they could turn the space into a bustling, book-minded wonderland, and the stock would change enough to make every trip a new experience. Call it Seattle Book Works or something like that, and you'd have a Seattle-centric institution in the making, a Pike Place Market for books.
Organizing the rent on something like this would be a lot of work, but the traditional bookselling model is obviously in flux. Better to organize a couple dozen booksellers in a modified co-op system than to go it alone.