Why not create a different card game?? That way, it would be easier to implement into XP.
One time, with minimal scripting, I made a game, very simular to Kingdom hearts. What happened was, everyone had a deck of cards. Enemies, allies, everyone. You drew 5 cards, and everyone then chooeses a card. Everyone then sees what card everyone picked, and it's placed in an order. Every card has a number. Then, the order everyone plays their card is determined by speed. When it's your turn, you can use your number to boost another card's number, or decrease a number. The numbre determines then potentcy of the attack, healing spell, accuracy, etc.
I liked my battle system, and it was a fun game.