While I really do like the idea, there’s no reason you can’t compete and win with off-meta decks in ranked. You’ll need to put in counter cards to popular decks but it’s doable. I only play off-meta decks and regularly hit rank 5 and even got legend once.
That being said, I wouldn’t mind a mode like this. IMO the best way to implement it is for the data to be collected about which decks have been played already. Once a deck has been played ten times in a month, nobody can play that list again nor can they play one with less than a 4 card difference from it. This way people can’t get around banned lists by making one minor change. At the end of the month the ban list resets. You’ll get meta players on the first day farming each other but after that it’s just pure ingenuity. I don’t know a way to make the data visible so people know how to craft their deck without it being banned already but perhaps there’s a way.