Steve:

Even with hundred's of lines the fastest way to receive is to Receive All and then edit back out the backorders rather than receiving one line at a time.

I'd need to do some research but I think you can import one receipt for multiple PO's.

To get the import spreadsheet you will need GV, which can also give you the Line number.

Not sure how this would save any time as they would still need to enter the quantity received for each line.

A better solution might be to go for a Warehouse Management System add-on, Lenmax or Link2.