If J is truly sold out already, I'm not sure what the rules are, if any, in the event of no-shows. The problem is that the gate would typically determine if there were indeed no-shows, but my impression is that gate agents don't have the time nor the inclination, and perhaps aren't even authorized, to go through the laborious process of "pulling" the award (or VIP) and then reissuing the ticket once they have awarded someone the seat that becomes available. In my experience, the Admirals Club personnel are best suited to actually process the transaction. So, to make this work you would have to have some degree of cooperation between the gate agent and the Admirals Club (or ticket counter).
If J is not truly sold out, then my understanding and experience is that it's basically first-come, first-served. If there are seats available on the day of departure, someone at the airport (I've personally had it done at the ticket counter with reluctance and I've had it done by the Admirals Club with pleasure) must first call inventory control and get one of the unsold J seats released, then they must hang up and call AAdvantage Customer Service to get the miles pulled and an award certificate number issued, then they must stand there for literally 10 minutes and type a bunch of stuff into the computer before the ticket can be issued.
I don't think the previous waitlist applies at all at this point; if there are unsold J seats, it's a matter of someone taking up your cause and putting forth the effort to call and get the seat released, then doing the work to get the ticket reissued using the award.