See Metabolt.

> "metamagic cards would be in boosters like checklist cards, so you don't need to worry about drafting them."

How about further expanding upon that similarity to checklist cards. Right now this doesn't actually serve any purpose at all exccept for rules text, but it doesn't actually help you to remember/designate your choice. I'd suggest suggest to have an actual checklist:

> "[ ] Lightning
[ ] Flame
[ ] Spark"

You don't ever need more than three of these since you can mark one for each choice.

The greatest weakness of this mechanic is "Imbue Metabolt". By allowing a single Metamagic to affect only a single card the choice is basically one of "which burn spell do your prefer to have in this format?" and that one often might be a more obvious choice than is interesting.

Further revealing that you play a certain metamagic would no longer pinpoint that you are playing a particular card.

How many cards had you planned to use this mechanic? As far as I can tell you don't even need to actually play the imbued card to be able to make a choice for metamagic, so a savvy player trying to obfuscate what cards they actually play or even the color of the deck might start the game with ten different cards If on the other hand you have a single Metamagic that affects a bunch of cards, then you sometimes might have to consider and make a meaningful choice e. g. you could have cards that only gain a bonus for one or two of the choices of a metamagic, so you have to consider which choice will benefit your set of cards the most.

That's why it says "You can't choose the same one more than once per match." Each game you're required to make a different choice, so at the minimum you're switching between two modes every other game (assuming you go 2-0 each match). This only really works for competitive play, though.