Google Maps Navigation
On my morning commute today there was a lot of traffic. I still use the Google Maps navigation feature because is identifies alternate routes when traffic on your current route is heavy. It pops up a message which says something along the lines of "We have found a faster route, would you like to change routes" with a yes /no option that defaults to yes after about a minute. If you do nothing, it will set you in the faster route, but if you prefer, you can continue on the route you're on.
Perhaps we could apply something similar in League. Riot already has a wide breadth of data on what kind of chatter is typically considered toxic. Could we have a popup in game that says, "It looks like you're starting to get toxic. Would you like to mute yourself for the rest of the game?"
This would give in game feedback that current behavior is unacceptable and offers an opportunity to cut it before the severity increases. It's not a guarantee that you won't be reported anyway, but if you get cut off early on it's less likely that someone reports you at the end of the game, which is a win for everyone involved.