I've made a couple suggestion topics for Balatro, but the Slot Machine joker is the one concept I cannot get out of my head. I can't code at all, so best thing I can do is post it here and see if anyone capable finds it interesting enough to give it a go:
Slot machine / Jackpot Joker (Rare)
If hand played is a Three of a Kind; all cards scored are randomized.
(Rank and suit, in addition to all modifications (edition, seal, enhancement + all modded equivalents) are changed to a different one of the same category)
Hidden mechanic "Payout": If hand played is a Three of a Kind of one suit; scoring cards have a 1 in 3 chance of getting a random enhancement.
Hidden mechanic "Jackpot": If hand played is a Three of a Kind of 7's of one suit; scoring cards have a 1 in 2 chance of getting a random enhancement, a 1 in 3 chance of getting a random seal, and a 1 in 4 chance of getting a random edition.
It'd be like playing with a continuously evolving erratic deck. Primary use would be either deck fixing by accumulating as many of the desired suit or rank as possible / hunting for the correct combination of enhancement, seal and edition, or hunting for the 7's Jackpot.
Only thing I'm uncertain of is when the card randomization is supposed to happen. If it triggers before card scoring, a really good card might change into glass and break. If it happens too late, you wouldn't be able to see what the cards turn into.
I think the best way is to have them change during the same step where glass cards breaking would be determined. That way, if you play a glass card, it still runs the chance of breaking, while if it changes into a glass card it does not. And you also get a glimpse of what the cards turn into before they head off screen.