We looked at doing this recently for a series of internal playtests, because we wanted to experience first-hand whether things like pacing or counterplay felt very different a few years ago. Unfortunately, we weren’t able to easily get the older builds running because so much of the game content and code has changed.

We can’t just pull in old data and expect the current game engine to play nice with it all. We could almost certainly make it work if we had a bunch of smart engineers working to make it happen, but then those engineers would not be working on other features that might be more valuable to you guys in the long run. Likewise, we could have designers create versions of existing champs that tried to mimic the old data (Season Two abilities, items, tuning, etc.) but that’s a mountain of work for something that might only be fun for a few games or so. In other words, the opportunity cost of that work is probably pretty expensive.

So philosophically, we aren’t opposed to playing an older version of LoL, and it might be fun for a short period of time (because we might very well discover that the reasons we made all of the Season Three, Four, and Five changes still exist), but there is a good chance it’s not worth the development effort that it would take.