Pretty tough to make that work in a way that doesn't severely annoy the FP holders. Get rid of a benefit that was advertised at time of purchase and is good for up to 15 months? Don't officially torpedo it but introduce bidding in a way that effectively removes the benefit and the smart FP holder is just as miffed. They would pretty much have to wait until T-24 hours to accept bids or there would be heck to pay with some high spend flyers.