In looking at the recent development such as Quarterback and Ikon, I had the thought that League players seem to want the ability to create objectives to make the game more fun/interesting. And that got me thinking, with games such as Dota 2 having a said "Custom Games Mode," why not release a game mode that either replaces a current game mode or is simply added as a game mode? Riot games, even in analyzing Nexus Blitz, stated that it wasn't popular enough to be a permanent game mode. But a Custom Games mode would be able to hold that spot because new content would be consistently created by content creators!
Think about it...
Essentially all Riot would need to do is make a blank square map. Then, in a Halo Forge-esque/Disney Infinity Toy Box experience, they would give players the tools to stick different parts onto the map. Then they could create different goals, what types of characters could be used, and the whole nine yards.
It could have a featured section and even reward BE for maps that were the most popular or voted for.
This would give us our race mode, 1v1 arenas, one for all, and whatever else one could think of.
To top it all off, the icon would be an anvil, and the mascot for the mode and tutorial instructor would be none other than:
And before you give me the whole "It would remove the profit of RGM that Riot would make," I have a counter incentive for Riot:
Why not just make different skins for the different objects within a player's toolbox?
The default palette would essentially just be Summoner's Rift map parts and perhaps some other additions. You could reskin those parts with different textures that cost Orange Essence. Heck, you could charge Blue Essence for certain novelty parts such as the catapult and establish prices for pieces outside of the original toolkit (just be sure to add enough pieces in the original kit for creativity).
Just spitballing here, any thoughts?