HKG and SIN are unlikely to transfer to Mixed Fleet because they use International Cabin Crew who work to Worldwide crew working practices (hence why the new EZE direct route has not gone to Mixed Fleet). The really plum long haul trips have not moved to Mixed Fleet.
BA is over-crewed at the moment. But might that have something to do with the ongoing threat of strike action? That should give those who are keen to go on strike pause for thought. If I was BA I would defroster any strikers for a minimum of three months to protect the non-striking majority from BASSA bullies. Any striking Pursers and CSDs should also be subject to rigorous performance management on their return to work.
If BA is the beastly, corrupt employer you claim it is then you would be better off seeking employnent elsewhere. BA does not owe you a living.