This is the game mode I'd like to see.
You can play any card you have at any time once during a match.
Instead of having 4 cards at the bottom of the screen you have 4 "wheels" where you can select cards from.
You can make "all cards decks" in advance where you choose where each of your cards goes (which wheel and which order).
Once you play a card, it disappears from the wheel.
What do you guys think ?