I have a suggestion, which would make a lot of people happy. As there are many "mid wars" in the game, where all players "agree" on only playing in the mid lane, there are always some bad mannered people, who just push the sidelanes or going to backdoor in later stages of the game. One might think, you can just kick them, but it is not often, that a kick vote goes through...
So i suggest an only mid option, like in DotA, where the outer towers are invincible and no creeps spawing on the side lanes!