I don't know if you can do this with AA (US has more flexible rules):
you can potentially fly Cathay first (you'd have to go to HKG and then back to Tokyo).
JL has a direct flight that is one-world. ANA you won't have enough miles for (it is 120-130k using United miles).
Singapore Air is also another option. Not sure how many miles it is, but they have the A380 from LAX to NRT.