Retro Character Model/Ability Mode

Just an idea for a fun game-mode that would be added in the same way as URF or Poro King; just for fun and curiosity. Ever since I've played League of Legends, I've always appreciated how even the oldest of champions can be updated with new abilities, balances, splash arts, and even visual re-designs. While that's all fine and good, I sometimes long for the old character models and play styles out of pure curiosity. I sometimes miss Karthus' old look and even Sion a bit. So what I'm suggesting is this; a cosmetic game mode where champion select allows the option to go back to old character models and play styles. Now, again, this would be a separate game-mode of its own since the option to simply choose from an updated or outdated version of a champion can interfere with the game's competitive side in regular matchmaking. I just thought it'd be a cool little game mode to introduce to those newer players who couldn't experience the classic look of some of their favorite champions.