Yes, this omits the people who already have a job and wouldn't want to quit just to freelance for a week. But I doubt this would leave out genuinely interested

Yes, this omits the people who already have a job and wouldn't want to quit just to freelance for a week. But I doubt this would leave out genuinely interested people who aren't employed. Assuming a preliminary acid test on the employer's side for skills needed and on the candidate's side for interest, this seems reasonable. You may want to have a Plan B for the employed.