Skins for XP
Champions should have milestones or XP markers that when you reach you get a skin or a cool recall animatoin. Also like little achievements if you land 1000 hooks on
you get an icon or maybe some new hands or helmet that would make the champions more personal. There's unlimited options with what to do but MW2 did this for its guns like you get a certain amount of kills for a gun you get a camo for the gun. This made the game more playable because you had things to reach but it kept going making more players come back and play for another reason.