I thought of something that might make this game awesome besides PvP.
How would it be to create a story-telling Gamemode based on the champions Lores, giving it a open world experince ( like Diablo for example), adding possible Bosses, Rewards based on performance ( Hextech chests/keys and Summoner Icons ).
Imagine what the people of Riot could create, thinking of how good they are making Cinematics aswell.
I know it sounds like a lot of work, but i think our community would love to do some PvE to cool of after an exhausting game in Ranked.
when it comes to the arrangement of the Campaign, i consider it to be done from Old to Most Recent, and creating Rivalry like the one Kha Zix and Rengar have.
Hope this gets upvotes!