The rules regarding transferring airlines in China are going to be relaxed shortly. This will benefit both contractors and local pilots.
The screening process takes 9-12+ months due to the back and forth nature and that each phase has to be passed before you can move on. But if you fail at any phase, you'll just fail at the same point with another carrier so there's no benefit to being able to apply to multiple airlines.
I can only imagine what it was like 10 or 20 years ago....