Take a teeny cut in your huge FSS pension to help the new guys, who may then help you down the line to fight for your retirement.
The days of the huge FSS pension have gone and a lot of people, myself included, do not expect to see the FSS last out our careers. Pensions are deferred pay. If you want to start robbing Peter to pay Paul one might reasonably ask if the DEPs coming in on £55K will be contributing to a hardship fund for the new SSPs who'll be doing the same job for less than half the pay? Of course not. The aim is to improve BARPS but nothing happens quickly in BA. Perhaps the next pay deal might see an improvement, especially given the difficulty the company are now having in recruiting suitable pilots.
Coming into BA with that sort of attitude is not going to endear you to your new colleagues. You may quickly find yourself pigeonholed into the 'whinging ex-mil FO' bracket like so many others.