Ideas that could help!
I know there has been a saying going around, "skins give ya power", why don't we have that very saying come true, where each skins provide their own unique stats/ mastery(Talents)/ passive; there was a another game that is only starting to implement this idea, but it has only progress to the stage of giving more basic stats instead of going further like specialty stats and the likes of other things.
Speaking of more unique stats, we also need more new runes, the runes we have now are only focused in basic statistical option(which is not bad, but become stale overtime), having some more runes that give something out of the ordinary isn't so bad.
More items for marksman (and only for marksman!!), the items that were introduced during the "marksman rework" weren't really meant for just marksman champ as they were easily exploited by many other champs that were melee, granted that having a lot of items be made only for marksman would solve little about it, but it will be a good start, having some items provide more benefit to marksman compared to melee champs would be another thing to add to this section of the topic (Example: ranged champion receive full value unique traits, while melee champs only receives half).
That is all of the ideas that i would say be a benefit to the game play, i'll check to see what people think about these ideas or read any ideas that they want to see riot implement into their game.