Hi it could be nice to be able to play in some rotating game mode an old version of league. I know it wouldnt be as fun or epic as some other rotating game mode but it would be nice for all the hard base of dedicated fan that sticked with the game for so long. It would also be great for newer player to experience what league was like back in the day. It could be an event over several week where people can play from beta to season 7. Passing through the different meta that shaped league of legend to what it became today. Kind of a yearly anniversary thing.
Its just that with online gaming, especialy an ever evolving game like league, it's impossible to play older version. And maybe newer staff at riot could discover a few things from precedent season like those new /old items that are brought back.