IDK, I think you should just add to the notes "if there is more than 1 card with this passive, then... [the 75% chance thing]", assuming the card is chosen randomly.
For example, if you have 3 of Card A and 4 of Card B, and both Card A and B are the only cards in the deck with the passive, then a random card out of the 7 is chosen for your starting hand and the 6 other cards with the passive have a 75% chance for each subsequent slot in the hand. That sounds pretty hard to code, though, since I'm sure the current code only randomizes the deck and then does the auto-mulligan if necessary.
Anyways, the mechanic itself can't really be used on some amazing, ingenious card that i can suggest. That's for the creative people to figure out. I'm guessing that there aren't many cards that benefit from this passive more than the rest, unless they're cheap quanta generating cards that aren't zero-cost. Of course, those are also boring unless you have an ingenious, new quanta generation mechanic in mind.
Weapon may be cool, since you can fly weapons.
