If you want to protect your pay, do you not just bid for all heathrow commands before your FO bids? You won’t have the seniority for a long haul command, so you will get your desired C32L, or an FO position with command pay. (I highly doubt 3100 will be senior enough for a long haul FO position with 140 more senior FOs on the 747, nearly 100 on the A380, and loads on the 777 which is also in surplus).