Rage quitting in ranked should be met with an automatic 14 day ban.
No second chances, no excuses. If it's blatantly obvious that a player rage quilted in a ranked game (ex: last game where my Eve got killed twice in her jg because she pathed like a bonobo and then proceeded to type "FUCK I AM SO DONE AFK" before leaving the game) they should just be banned. Proceeding to do this again should be met with a permanent ban just like the instant feed back system.
I don't think anyone in the League community would have a problem with players deliberately fucking over their team's efforts to win just being removed from the game entirely. It boggles my mind the amount of rage quitters I've encountered in Diamond elo. I've legit just had to open at 4 minutes because of a fucking buffoon.