Imagine having an open world league game where you chose a character of your choice and can experience their story. Go through their storyline and basically get to know more about that champ by playing through their eyes.
You can roam with other players throughout Bilgewater, Ionia, Noxus, Demacia etc , create your clubs, trade and sell items (clothing/chromas perhaps?).
I can imagine kindred, roaming to collect bounties or having to hire assassins to help do missions for your city. Travel to various unlockable cities and basically bring league of legends in a new way.
Now how many would pay to play this lol