I don't play too much anymore, but I'd add back URF, Showdown, and One-For-All (the one on ARAM) in a heartbeat. As for changing the core game, I really have no idea. I'd try to make the game a little more snowbally than currently is so the games could last shorter (I wouldn't make it as snowbally as it was in S3 where a Riven with a few kills would be GG, but a little less than that).