It annoys me to see a first time Yasuo player take them straight into ranked, because they bought a skin or were just yolo. Make it a requirement to at least play 5 games on the champion in a normals summoners rift game before allowing the person to play that champion in ranked.
I've actually been advocating something similar, because of all the people who queue in clueless how to use their champ and decided its okay to try a first-time champion in PVP with a 10/10 difficulty level.
My idea is that all champions must be played five times and win five times in any intermediate co-op mode before being unlocked for PVP. That will be around 75 minutes or so in which they can learn what champions can and cannot do and helps them actually not die repeatedly because of not understanding the mechanics in five seconds flat. Everybody with champ mastery 3 and above is "grandfathered" in and doesn't have to worry, but level 2 or below or never played? Five co-op Int bot victories or no PVP unlock. Simple, efficient, and guarantees people this person at least played a few games to cut down on the feeding and such.
