Sure, the possibilities are endless with those types of routings, but we've got enough problems upgrading on CO metal, I would find it hard to believe that CO would allow an upgrade of an AS/VS itinerary.

I had a similar issue when I looked into a EWR to AKL (fly co to see...Aukland, NZ ) on US Air. Even though Quantas listed an EWR/LAX/AKL routing if I wanted to fly Biz using miles, I would have to fly US with a domestic connection to LAX, i.e. NYC/PIT or CLT/LAX/AKL.

Have you tried booking the tix w/ CO, NW segments as part of the itinerary? CO/NW have direct flights from SEA to all of their gateways.