It would be great if you could make it so you can only get certain cards depending on the ball and cards you're using. Like if you don't have poison and aren't using scythe then you shouldn't get any poison related cards. The same could go for the summon cards so you can't get them until you get helper scepter or potion. And maybe if you got spectral weapon you can't get critical parry and katana's merit and it would work the other way around too, or just make it so if your weapon makes contact with the opponent's weapon it gives the effects still.
Also I don't think mine and lantern should be able to get bounce cards since it literally does nothing for them.
These are just some ideas and you don't have to add them if you don't want to.