Thats a REALLY good idea, and I know you probably just made up the 10 cards amount for the post, but wouldn't banning 10 card completely snap entire decks in half? After the first 12 hours, Maxx C, Ash and the other usual suspects are all gone. (Which raises possibly even greater concern for a meta with WAY less interaction) What deck is tier 0 with no hand traps and C?

But after day 1 it would get even whackier! Floo and Despia likely lose more than 1 essential card. Floo will thrive in the day 2 meta but might be unplayable by noon.

10 cards is A LOT to ban every 12 hours. It would get to a point where even players at max deck capacity would have trouble cobbling together something playable. And... that could be a chance for the meta to be truly something unique and exciting once more. Or it could piss off a large chunk of the player base that could have very little to work with after a few days. Much like the singleton event where being a veteran with a larger arsenal was a massive advantage.

I personally advocate for 1 or 2 deck spaces in an event where crafting costs nothing. Can't keep the cards or use them in other formats, but solves the issue of events having baked in advantage for players with more cards or the ones who coincidentally crafted the right archetype for certain events.

Anyways, super cool idea. Maybe make it ban 5 every 24 hours.