Indeed, I am sure for many a trial period wouldn't be acceptable, but companies should give those that show potential a choice if the alternative is an outright rejection.

Agree. There might be some nasty adverse selection bias for the employer as well. Those who are at risk of getting fired at their current employer will probably jump ship for anything, and those who are rockstars (to use a cliche) won't worry about the auditioning process. However, those in the middle, even though they would probably be great employees, might not take the job due to risk aversion.