Adding the Belltown stop may make sense, the legal profession always wins. Killing Sounder North but not mediocre express bus service is unfair. ST Express tickets can be purchased with the Transit GO Ticket app. Keep it local and relevant.
Even so, concessions, there are also some bus stops and taxi lines outside of the airport that could transport you to any destination within the city in case that you need a ride with more privacy or if you have too much luggage.
Link station at Dravus St that would allow workers in SLU and the north end of downtown to get to their jobs without a long trek down to King Street and back across downtown on a bus..