You have identified many of the key issues in document scanning. Slipsheets and barcode stickers are widely used in the industry. Digital cameras with grunt labor turning pages is reportedly the way Google is scanning books. Your best bet is probably to buy a $400 personal desktop duplex scanner at 20 ppm and feed it patiently. This will take a long time. But I think that for production-scale scanning of mixed material you are way over your head. If you expect to simply drop in a stack of papers from your file drawers into a high-speed scanner and walk away you will be very disappointed. This is why there are document scanning services in most metropolitan markets. Your desire indicates a latent market for a roving document scanning services that will come to your home or office and do it all in one day with highly engineered equipment and processes. The question is, what's the value to you, so how much could they charge? The pricing would probably have to be above the value to consumers (who value personal time cheaply) but to small businesses going digital it could be worth it. I'd look for this service coming into existence in the next five years or so.
-Eric Saund
Area Manager
Perceptual Document Analysis
(Xerox) PARC