I like John's suggestion. To do this right and well, you're going to need some gear. A rig to hold your camera(s). I've seen arms for cellular phones too. Its just depends on how fast you want to go.
On an aside, I have used both of these personally. These devices do exactly what you are looking for. They also support flattening, scaling and automatic numbering. The higher end model has a cool foot pedal. They are not cheap, but if you take your time into consideration and have a large amount of data to scan/archive, they do work really well. Just throwing it out there.
Another option:
