Well, if a 6th (or more) legendary jokers get added, I might as well give more suggestions.
Feste
Effect: Copies every joker's ability and retriggers all cards. This joker's ability cannot be copied, nor can it copy any jokers that can copy other jokers, like Blueprint.
Rigoletto
Effect: If you play 5 cards that does not win you the blind (cannot be a boss), destroy the 5 cards you just played and gain money based on their face value. Face cards give $10, Aces give $11. Each enhancement doubles the money gained. The effect can only be triggered up to 3 times before this joker is destroyed and giving you $50
Pomni
Effect: +1 hand, +1 discard, -1 hand size, allows you to see the next 5 cards in your draw pile. This Joker is a negative by default
Touchstone
Effect: Lets you reroll the shop up to 5 times as you want for FREE, then you will need to pay the regular amount that you would need to reroll after the 5th time.
Puck
Effect: Every enhancement you have on a card or joker, gain x1.1 mult. Having more than 1 enhancement will stack.