I just want to point out that you may be able to do something like this with filtered decks (one of the buttons in the same row as stats on the deck intro page). I know you can filter decks based on tags, and generally on a search string. I believe you can search for a particular card by name, to filter for only those cards. The nice thing about filters is that it temporarily creates another deck based on the search that you can empty and rebuild. The cards are either in the home deck or in the filtered deck, but you can easily go back and forth. You just create two filtered decks, one for front first, one for back first, and then you can fill/empty them as needed. The assumes that the home deck simply has two card templates in it, one for each direction. Also, I'm only assuming the ability to filter by card type is present. Entering something like "card:FrontFirst" if you name the card template FrontFirst would pull up those cards.
--charlie