Do you think Willie might just think to hell with out and outsource cabin crew given all the headaches they give him? TUPE them all out to some joint Iberia / BA thingy so he has comfort in numbers and then go to work on all the Ts and Cs until he gets the workforce he needs for the costs the airline can afford.
While Ts and Cs will transfer on day one of the transfer they then become fair game for change - and the new outsource company (European Cabin Services perhaps) would have no existing union agreements to adhere to.
His patience must run out soon.