Scope is about security of employment first(and its immediate secondary effect is on securing reasonable Pay) not just outsourcing to the current cheapest option(not to be inferred at the BACX Pilots themselves).
If BA succeed in hiring the lowest cost operators at will for their operations, eventually their choice of operators will spill over to include other country Operators as well. So 10years down the road when Pay Negotiations are due, BA will say;
" sorry mate, we just had an offer from Ukraine-express(then part of EEC) who will do it for half that and put their Pilots up overnight in the UK at the bedsit they own, Yes I know a one-bdrm flat in the UK is 500,000 pounds so what, you should have agreed to SCOPE when you were at BACX !!!'
Without Scope we are wide open and any Pay Negotiations will not be worth the paper written on. Yes you can have a 20% Pay Rise but we will start outsourcing 80% of your jobs and your headcount will continue to fall off a cliff.
I think you get the picture.
Everyone is worried that Scope will cost them their job now, when in reality it will protect their jobs for years to come, despite unpleasantness now.