I'll be honest here. This won't work just because of people who care about winning too much. I mean, we have ARAM that's supposed to be a fun, relaxing 'mess-around' gamemode and what happened? People are literally making ARAM-specific accounts and buying all of the champs that are gods there (like Lux) so they will more often than not roll a champ they can stomp with. Hell, when URF first came out it was fun for about three days, and then people discovered that Heca and Nid were OP and started spamming them 24/7 unless they got banned. And when Riot perma'd them, they moved onto shit like Sona. And then Riot perma'd Sona and they moved onto something else that was disgustingly OP. I wasn't around during the second time URF rolled out, but from what I heard it was even worse. People didn't play to have fun, they played like it was their Ranked promos and they needed to win at all costs.
Long story short, tryhards in fun gamemodes is why we can't have nice things.