I really like this concept. I've actually been wanting to try something in a FPS. I like your animations and the punches and attacks feel satisfying when you land them. It could be beneficial in the future to show a light overlay in the area where the attack or movement will take place along with maybe making clear where the enemies will be moving to. I think there's a lot of room for expansion as well, maybe with collecting more cards and creating a deck exactly how you like. I think with some clearer sprites and tweaking this could be really great!