There are certainly many ways to attract people to Tacoma. Museums may be one but I contend that money is another. That's right, the color of money as in more if it in one's pocket. Picture a small-ish ferry dock just on the Thea Foss waterway somewhere near that gravel lot in front of Johnny's. Tourists can stay in an affordable hotel here in Tacoma and grab a foot ferry up to Seattle. Once there, they'd bypass the freeways and parking hastle and be dropped off somewhere below Pike Place Market where they can stroll around the best parts of the Emerald City unhindered. Sound far-fetched? Why? We've got the water and now a couple hotels downtown. Not only could visitors wander the most well-kept portion of Tacoma from Pacific down to the Museum of Glass but they'll be able to find more fun and even spy some scenery by taking a boat up to Seattle. At some point it would be nice if the Link light rail ran down Dock Street to make a couple stops for the museum, condos, and this ferry dock before heading toward Old Town.
Keep the prices reasonable make the boat cleaner than the [actually pretty nice] buses and you'll have plenty of day-trippers take advantage of it. I'd certainly sign up seeing how little I get to Seattle due to my own aversion to traffic and/or strange people on buses. We've got so much beautiful water surrounding us that I think it's a shame more people can't enjoy it without having to own our own boat or be fit enough to canoe or kayak. Anyway, it all, as I mentioned, comes down to money. Saving tourists a few bucks is one thing. Expecting the city and local business leaders to caugh up the green is quite another.
P.S. - Did someone say Kalakala?