Reworked Champions
While League has been an ever evolving game some champions have been reworked that changed their core identity as a champion, (Mord, Sion, Poppy, Aatrox, etc). While I agree that some champions kits have been outdated as the game has progressed there are some players who don't like the reworks to the champions they have grown to love.
I would like to suggest a game mode that would allow you to play the old versions of champions. It could be called League Legacy or something. Whether this game mode would also include old items would be a difficult decision, since many items were removed because they were broken with some champions, I'm looking at you Udyr and Enervating Locket, and other items were just unbalanced (DFG).
Personally I have missed old Mord, Aatrox and even Urgot. I enjoyed playing champions my friends told me were bad and trying to find a way to make them good. i found out that Aatrox as a jungler could solo Baron at 20 minutes with 2 items and boots, Urgot was the ultimate top lane kite champion, and mord did some of the highest damage in the game at the cost of mobility and CC.
I'm not saying we should revert all the champions who have been reworked over the years, but having another opportunity to play those champions that have been changed forever would be a fun and nostalgic experience.
( <- From what I hear at least) and
Most of them would've made fine NEW champions (except Akali, screw new Akali), but they aren't really anything like their old counterparts.