Nice thought, and maybe it would work, but I somewhat suspect ticket agents dealing with the crush of holiday travel wouldn't have the time or resources to figure this out. Also, finding a day-of-departure upgrade available to a (presumably non-status) passenger would be tricky at best.

I usually send an email around to friends and extended family asking if anyone has flights planned on AA. Alternatively, maybe you can try getting in touch with local charitable organizations (Make-a-Wish, veterans' orgs, etc) and see if they'd have any beneficiaries who could use the upgrades for upcoming travel.