There could be a big cost saving if you don't need horrendous levels of standby cover.
You may be right but it is not me that you have to convince but both BA and your colleagues. If you truly believe it will save BA money, put together a Business Case and put it to them and if it does make financial sense they will think about it. Of course you will have to persuade BASSA of the advantages of a bidding system and they have a long history of resistance on this matter. It is also worthy of note that if the savings were self evident BA would be pushing for this too. They had the perfect opportunity to implement it with MF and they didn't which suggests the savings are not there for BA. BA are fully aware of the costs and benefits of bidding as they have had it for the pilots for years.