Feature Request: Dual Card Handling

Most current prosumer and professional mirrorless cameras have dual card slots and support recording each image to both cards to guard against card failure or corruption. In addition, I find that if I forget and leave a card in computer's card reader after transferring images, I still always have the other in my camera. 
It would be helpful to add the ability to add the folder containing the files from the second card to the current view, but in an intelligent way that recognizes the relationship between the two folders. For example, there could be several helpful view options:

• Show only folder/card #1
• Show only folder/card #2
• Show/Hide images present in both folders/cards
• Show/Hide images in folder/card #1, but not folder/card #2
• Show/Hide images in folder/card #2, but not folder/card #1

This would make it easy to either assign an XMP label to designate images that are only on one card, so they don't get missed, or to copy all unique images to a new "working" folder. If a label is assigned to an image in both folders, and "Show/Hide images present in both folders/cards" is set to "Show", both files should get the label, but if only one card is being viewed, only that card should get the label. The "copying unique images to a working folder" idea only really works when the version from just one of the cards gets copied.
In the future, there could also be a compare function to see if any image data is different, which might indicate one of the files has corruption.