Lol mapping playing cards to MTG is wild.
I was thinking that you'd be allowed to play a 1 on turn 1, a 2 on turn 2, etc or maybe you start with (turn + 1 amount "mana") or something. But I was thinking it'd be a resource separate from cards. I agree that if you can just play whatever whenever, then there's no reason to take non-face cards.
Different suits would allow for ways to make use of that resource differently. To play a card to the board from your hand, you usually use the equivalent amount of the resource.
For spades, maybe that's from your hand or from your discard pile. Maybe you can discard any number of spades to draw that many cards?
For clubs, maybe you have an option to play cards that "generate tokens" (all at once? Each turn?).
For diamonds, maybe you can't play anything to the board until it's a face card, but your non-face cards can be played tapped to bank resources that can be cashed out via sacrifice later? Or maybe you can play cards that are in some way benefiting from your opponent's cards to ensure you have good value?
For hearts, I was thinking of more of a grafting mechanic like auras in MTG, where playing something consecutively higher than another could get you one beast with the sum of those ranks?
Lots of ideas to play with here, and it's hard to tell on paper which of these is or isn't balanced. Similarly, it's hard to tell if 13 cards of one suit is sufficient, if aces should be high or low or both, if decks should be drafted from all 52 cards at the beginning of the game, if multi-suit decks are encouraged/preferred/not, etc
