In 2012 I was told Google gets 1 million applications a year. How do you decide which 1000 of those get 6 month contract offer? How many millions of dollars in lost productivity are you willing to lose of the people who don't pass your 6 month test that you had wasting space, taking up training time, having people have to review and reject their code, etc? What will those people do who gave up their lives somewhere else to be part of your company do when you tell them you've decided to not make them employee when their contract is up?