In case there isn't anyone who doesn't know the concept, in MtG, if you don't like your opening hand, you can opt for a Mulligan where you shuffle up and draw one less card. Could this be implemented, if instead of having 1 less card, you had took the eighth slot and put in a card that was something like:
Mulligan
0- If this card is discarded, the next card will be this card.
You could make certain cards overwrite this if you wanted, like auxillia for instance. It could be at the beginning of the game, you'll have the option of mulliganing before you see your opponent's cards. You'd probably have to make it doable only once per game in order to avoid people trying to get really good rares (although the chances of that not working and screwing you over are pretty good).
The main downside is that it would take longer to set up a game, but it could add another level of strategy.
Could this be implemented? Would anyone else be interested in that kind of feature anyway?