Just curious as to how the payment part of this would work? It's a great idea - something you could build out (a vetted list of top-quality freelancers available to work on your project? People would love that).
If there is a vetted list of freelancers all of the same, trusted, standard, it could be that having individual minimums creates a 'race to the bottom' thing that other places have. I would have a fixed price per hour which is slightly above average, with a guarantee of high-quality return and efficiency.
If you can get members to work with and look over projects they're not attached to (feedback etc) you could increase the value of the service as a whole.