Game mode/Client that runs old patches?

I was thinking that Riot could add a game mode that allowed older versions of the game to be played, such as an old patch from season 3 or 4. Does Riot even keep versions of the game that are that old? I really enjoyed the game back in season 4 which is when I started playing and I think it would be fun to be given the opportunity to play on the old summoners rift with the normal drag. What are your thoughts on Riot adding this as a game mode or separate client just for this?