I have not run into any other users asking about this functionality. If you could post the suggestion in the wishlist forum, the product development team will take a look at the suggestion for a future version of the product.
What you're proposing does seem to be a valid way to accomplish this. One issue that you could run into would be if one of the credit card transactions errors out, but the others go through. You would have to take that into consideration when setting up the behaviors. I'm not sure what other issues you might run into.
You would also have to create receipts for each of the cards and store the payment information into the database multiple times for the same receipt. When displaying the order history, you would have to check to see if the user used more than one card.
If you have any other questions, I can try to help you out, but since the behavior is not part of the supported behaviors of the product, I may not be able to help you out. There may be other users on the forum that have worked on something similar to this before and may be able to help you out as well.
