I think that airline "protected rebookings" work fine. It's one of the more important benefits of status on AA. Yes, there will be two (duplicate) bookings for a brief time, but this is not as problematic as it seems...

The standby process should eliminate the inefficiencies of double bookings. If the ticketed passenger is still absent at T-15, the seat is given away. If in business class, the next in the upgrade queue gets a battlefield promotion, and a standby economy pax accompanies the GA to the plane for the vacated economy seat.