>> Provisional employment does not work. It requires candidates to leave their jobs before they know whether they have a secure job with your firm.

It works. I’ve seen it in two different places.

At the second one, the fundamental realization I came to was that it is virtually no different than “regular” employment, where the new employee can get fired for not meeting expectations within an arbitrary time period after being hired. This can be months, or even weeks. From the perspective of the candidate, regular employment and provisional employment have roughly the same level of risk: in both cases they take a job where they might be let go at some point. The benefit of provisional employment is that they know how long they will be evaluated for and against whom. It turns out a lot of candidates do in fact like the all-cards-on-the-table approach and enjoy being given the opportunity to prove themselves on the job.