Here's a likely unique take, that will develop over the next couple months:
I play an online card game called Gwent. Those familiar with the Witcher series of video games may recognize it as the game-within-a-game from the third installment of the series. The standalone game that released after TW3 has gone through many changes, and is soon to receive an overhaul in the upcoming Homecoming update.
There are several major changes lined up for Homecoming, one of which being how deckbuilding works. Currently, decks can be any number of cards between 25 and 40. Certain cards are classified as gold and silver, and each deck can run a maximum of four gold cards and six silvers. As you may imagine, 90% of decks run four golds, six silvers, and fifteen bronzes.
In Homecoming, the system will change to a "provisions" system. Instead of having limits to how many of each type of card can be played, each card will have a provision cost and each deck can only contain so many provisions - not entirely unlike your suggestion. More powerful cards will cost more provisions, and vice versa. We still don't know everything about the system - they're still hammering it out and not everything has been leeked yet - but reports from people in the PTR are positive.
Now, I personally think that this system will be fantastic for Gwent. It allows a very granular way of buffing/nerfing cards without drastically changing their power level - just make them more expensive to include in your deck.
That said, I'm not sure I like it for Redemption, for reasons that other people here have pointed out. New rule changes already take a while to trickle out to those who don't use the boards, it's yet another hurdle for tournament hosts, and perhaps most importantly, we can't change the cards to say it on the card.
I like the idea of this type of system, I just don't think that it's viable in Redemption. If a "Redemption 2.0" ever happens, I could maybe see it, but not under our current system.
