That would be a neat solution but I haven't seen one. It might be hard
to write because it would have to be a client solution that could
interface with whatever scanner you have installed and I don't think
that there are standards there.

Of course, they can save  the scanner output directly into the document
library using WebDav, however, it won't prompt for required metadata.
They would have to subsequently go into the document  library to fill out
any additional  columns.

We've had good success with the HP Digital Sender products and the Autostore software for Microsoft SharePoint.

One nice feature is the ability to enter a small number of basic property values on the Digital Sender's LED screen that the Autostore software can store as SharePoint property values associated with the image.

There's a number of other solutions  also available on the market. Autostore also supports other scanners

I should also mention you really need to understand the customer's requirements before select a solution. Parameters like

a) size of the paper back file  (#documents, #pages, page sizes)
b) ongoing daily/weekly/monthly requirements in terms of #documents and #pages to be scanned
c) bar coding requirements
d) records management requirements for the hardcopy after it is scanned
e) document  quality, etc.

Looks like we are going to go with the
KnowledgeLake solutions  product line called Mozingo. It seems to
have all of the features we are looking for...