Having read BA' proposals, unlike most of the people commenting here, the changes to the Disruption Agreement are by themselves untennable. Crew would not have a fixed roster anymore. Just a change of wind or a few spots of rain would be enough for BA to invoke the new Disruption Agreement and your forward roster goes out of the window.
BA's plans are to make crew on 75% contracts work much harder. A clue to this is that only downward changes to contracts are on offer from BA at the moment.