This would allow some cards to be slightly higher powered, without it completely breaking the game. Thoughts?
I can't say how this would work in practice, but it seems like it could prevent people from stuffing the most powerful cards into a deck while
My thoughts are that whatever you add or change should be there only to either achieve the goal within the scope of the game design, or to solve a problem that hinders that goal. Just that principle alone would disqualify most of everyones ideas, but on a sound ground
It seems to me that the problem you are solving with the idea is "overpowered" cards. If that is the problem, then the solution is to revise the cards
so they are not overpowered.
Being overpowered in relation to other cards is, I'd suggest, inherently a design flaw that is even known from the get go since we also restrict the copies of the card to magically balance it out. And there is also the issue, I think, that you can't
actually balance it out since it just adds more random luck and card fetching to the game as Nico also touched upon.
Whoever happens to fetch or draw his/her "OP cards" would be at a to huge advantage. Why? Because of skill? No, because of sheer luck, or them building a deck around the OP cards. Because the cards are OP. Yeah, there would be some deck mis-matches where the deck with OP cards will lose, but in general, a card is OP because it brings very huge advantages. It will, by definition, inherently more often lead to a win than not. What does that add to a game? What does it solve that wouldn't be solved more elegantly with some other solution?
Furthermore, say that all of the above isn't so: The fact remains that suddenly you have a game where you opened the door to balance
power of cards and their impact by limiting the amount of copies (instead of, say, doing it by gold cost, pre-requisites to play them, negative abilities etc). When you start doing that you seem to believe that it actually limits their power (it doesn't - when in play, they are in play, and it's irrelevant that you had a low chance of getting them) and, more importantly, you will eventually get too many of those cards for it all to be able to make any balancing sense in unless one accepts that the randomness in the game should play a (bigger) role.
As for gaia.li the rarity won't be used for the reasons above. I don't think that what I write necessarily applies to all CCGs, but I really think it is an important topic that, depending on the gamedesign, could either add something (even if I don't see what) or open up pandoras balancing box.