Part time pilots is NOT good. For OBVIOUS reasons. One of them is the reason BA stood up - safety. I agree with them.
And at what level of full-time flying does it become 'safe'? The maximum? O'Leary & co will be laughing to the bank if that is the case. It is not, and much lower levels of flying have been achieved safely by persons with lower hours both within BA in the past, and on part-time lines at many other carriers.