The Idea: Reporting people for Unskilled demotes their level
Yes I know this idea would need a lot of work to make sure the reports are valid and such but seriously, imagine it. If people lost levels because they played like a level 5 would play but they were level 30, you would have less people trolling games and actually learning the mechanics. Don't ban them for it, just demote their level. Even in normals, because that is where people should be practicing and if they aren't playing right there, they definitely won't be in ranked games. I really believe that this would cut down on most trolls and would make people understand how 'everything' works in the game properly.
I do understand this would cause some issues because you can't know everything. Heck, the only reason why I understand most things is because I have been playing for 3+ years and I don't know everything, which is why I am expanding my knowledge by playing ranked. I know you won't know everything but the common sense things, such as when you are building health and resistances - you are the tank, you shouldn't be running from fights unless everyone on your team is dead.
Just a 'work in progress'. Hope someone from Riot reads this though.