A solution to increasing champion diversity
nerf the hell out of junglers. there now you have champions other than ones who can deal with a 1 v 2 turret dive early being picked.
there is a reason why all the top tier picks are the ones that can best deal with junglers, it's because junglers are far too strong for far too long in this game. your jungler decides whether you win early in 15 minutes or sit at your inhib turrets for 35.
let's start by nerfing jungle exp by 30% and lowering jungle camp respawn timers by 30%, and completely remove all catch up exp. now junglers will be forced to take a risk falling behind when failing a ton of ganks like other laners do when they roam.