Be careful how you bandy the word "scab" around. For those of us who have lived, worked, been fired and rebuilt careers it is a very emotive word and applies to a very specific group.
A recruitment ban is a good start. It will not be 100% effective but it will have an effect and unlike our last attempts at this the world market has moved on.
If you look at who is applying to CX these days it is the bottom of the pile. People other airlines have rejected so obviously not the 'cream' and certainly unaffected by any union reprisals.
But certainly worth a shot.