Two weeks ago I flew to Europe with my wife. I requested SWU and was waitlisted, I also logged in and requested X upgrades since we had a long AUS-JFK to make the EU flights. The X cleared, then two days later the waitlist cleared. In this case, it would've cost me 3 stickers to have my wife use X. So I called the EXP desk and they changed it to use the SWU for our domestic flight. In hindsight, this is how I think it should be, just give me the best opportunity to get the upgrade via any instrument, and in the case like this, I'll just sort it out once all instruments are exhausted. I think that's better than playing instrument lottery like I did on the original post's flights.