New game mode choose role/lane - random champ
I've always liked all random games, like in DotA. There should be a game mode with an option to pick your lane/role and then everyone random's a champ. I understand there are issues with masteries/runes being right so there might be a way to work around that. (I'm just too in the clouds to think of something right now 420blazeityolo)
In conclusion, I think a random champ element to a summoner rift map would be fun.
P.S. There was also a game mode where you could random 3 champs, then you have to choose from the 3 that fit the masteries/runes you picked.