Distributed Proofreaders already has some infrastructure set up for proofreading and editing OCR'd documents. It's not quite the same as your proposal, but the

Distributed Proofreaders already has some infrastructure set up for proofreading and editing OCR'd documents. It's not quite the same as your proposal, but they do track stats and have levels of participants based on skill and experience. Might be worth checking out. http://www.pgdp.net/c/