This game has a lot of potential, I think one change that could elevate the gameplay is lean into the deck building aspect. if you kept pieces forever until you used them, it would add a bit more strategy.
OOOh this is a good suggestion. I had it working like that initially, and I'm pretty sure I only changed it cause I aesthetically liked them all flipping at once. I was considering adding in something like what you are saying, with the addition of "limited edition" cards that only last a round, so there is a mixture of both systems.