[DoingIsLearning]

There are a few issues with the scenario you described.

For health and safety, security and tax purposes you would likely not be able to have an extended period of more than a couple of days without some form of contract for that 'trial' period.

If you are an 'established' professional then you most likely would interview for a new job while currently employed. So even in the remote scenario that you would take a couple weeks holiday for a 'trial' you would likely violate the contract with current employer by signing a 'trial' contract.

This would only work for junior positions or for senior professionals who have taken some time away from work. But if you make this a part of your recruitment process, there is the risk that you are discriminating against 'currently employed' candidates.