Good idea. Anything to complete with Blockbuster makes me happy. I had a similar concept for a video store, except you'd actually 'buy' the DVD and if you returned it you'd get a credit towards your next rental/purchase. You would not get credited to your credit card, as, the chargeback fees would be too high. Video's that were previously rented would sell for a lower price.
Idea was just another way of selling Used DVD's basically.
It has flaws and the business is tough so I don't plan on moving forward with the idea, but, it seemed good to me.