I like the idea, but to keep things fresh I would go the other way like in hearthstone. They have a 'wild' mode where all cards are permitted and a standard mode where only cards from the last 2 years (I think) are permitted. This makes it easier for new players and old players still get to play with their old deck if they choose.

The leagues run side by side so you can compete in both or just one. You receive rewards based on the highest score you get in the two league.