An idea to combine Champion Mastery and Missions.

I personally think unlocking level 7 on a champion feels really good and the in game emote is a nice way to display the time you've put into the champ; however, I think an unlockable quest line for when you hit mastery 7 could be really fun, make level 7 feel more rewarding and let players continue to be incentivized to play their favorite champs.

When the quest line is completed maybe the player gets a champion specific icon. The characters portrait in game could be used and Riot wouldn't even have to get new art made they'd just have to use resources they already have. Giving the players something with low cost to Riot and what I imagine wouldn't be too much work. Or even just a chest after completing all of the missions would be great. I've heard a few complaints about people not being able to unlock a lot of chests because of their small champion pool or other issues, and this could reward players who are really dedicated to a few specific champs.

Another idea for a reward they could give out is a champion specific emote. Or maybe a small bundle of emotes displaying just basic reactions/emotions of each champ. This would give players another way to display mastery, and customize their emotes with their favorite champions. That is if emotes even launches into the game, I saw it got some pretty negative feedback even if I think if done right could be pretty cool.

Riot already gives out a ton of free stuff through S ratings earned on champions, Rank, Honor, and the events they do, so I shouldn't be asking for more free stuff but I think it would be a really cool way of making putting a lot of time into a champion feel more rewarding. I might be a little biased though because honestly I just hate flashing my mastery 7 icon at people, it feels way too cocky for me, and I'd love a different way to show my love for specific champs.