Great suggestion, and I wondered that myself. I'll google for AS change fees on Award flights and see how that works. If you can cancel the whole ticket up to 3 months out, I can't imagine too much drama for adding a flight. Thanks.Can you book your HKG leg and then add REP in 2 days?
UPDATE: Again, google makes it easy. No fees for changes and it's up to 2 months out with no fees. Tried to paste in as an image and I couldn't get it to work. I'd think it was me, but a new user also has a "no img" icon showing. Did search get fixed but image upload break?
Anyway, apparently no fee for the change.