Would never work for pilots....
If a airline went down the road of casual pilots 1 of 2 things would happen....
1. Company would have a heap of extra 6monthly sim checks to cover as all pilots would need a current OCA check for that particular operation, as well as Avsec, DG and other required flightcrew training. I doubt any company would do that....
or 2. Casuals required to pay for their own 6 monthly sim checks, Avsec and DG currency, and that would not be economically viable to anyone, so a lack of casual crew supply would negate the need.
AirNZ maintains a pool of casual staff, mainly from experienced ex-full-timers wanting a reduced work lifestyle. Any newbies are usually full-time temps on 12month contracts with option to apply for fulltime. Very occasionally there isn't fulltime jobs for the temps at the end of 12months but mostly they'll get picked up or finish of their own accord.
S2K