Alright, I'm coming back to this since I have been playing games with a card-like combat system.
1. Operator Skills. Those are essentially skills that aren't cards, they are bound to a button. They trigger skills, like "Draw 2", "Reshuffle", "Discard", but they are not cards (a bit like the button common event plugin that used to be around in a previous update). They can have a limited amount of uses per battle instead of costing MP or something else.
2. Card Rating. I know you can make the cards look different, but I wish to add functionality to that. Say that you have a "Star Heal" card (and you use Star to refer to rarity), that consumes another card and causes healing dependant on the amount of Stars from the consumed card. The Rating of the consumed card becomes a power source for another card, which is then discarded or removed from play.
3. A feature to lock certain actors from having their decks edited by the player.