If Riot did a crazy huge project, what would you like it to be?

I personnally would dream of League Editor.

Create your own maps in a Warcraft3-like editor, where you can create two or more factions (3v3v3 maps? whatever you wish) , choose their number of players, nexus emplacements, number of lanes, minion pathing, create your own jungle camps, personnalize the buffs, stats of monsters, and also personnalize obviously the map in general : type of terrain, height, forest, walls etc.

Think your map makes a certain combination of champion/items OP? Create your own map-specific balance changes! Adjust every champion's base stats, abilities cost, range, numbers, ratios, tune the items yourself. Always wanted to know how your favourite champion would fare with your own custom made balance changes? Test those with your friend on your personal map, which can be even a simple copy of summoner's rift with a few changes you made.

One could even implement map-specific tuning for runes, and maybe even champion creation (!) Would be harder, since unlike war3, league doesn't have other models and ability/projectile models than the usual heroes, but who knows?

Overall, it would be so insane I'd pay without hesitation for this XD