Aleph mentioned a mirror joker that while being a good idea, the practical use was like a worst blueprint which if you just copy another cards ability is kind of bad game design
My idea is that instead of copying a random slots ability that it is a TWO PAIR joker where if you play a TWO PAIR with nothing else you get a boost (Im bad at balancing so you people can deside the numbers)
(Idea 1. Upgrade 2 pair/random hand)