If you do you will fall seriously afoul of AAdvantage terms and conditions. That could have the buyer denied boardung until they paid full walk up fare, and risks the seller's account closure, loss of miles and status.

We've seen how active and clever Corporate Security / AAdvantage Fraud can be.

This is not an option, and further discussion of how one might accomplish runs afoul of FlyerTalk Rules.

JDiver, Senior Moderator