Please don't take this offensively, but this is a gross misunderstanding of business, and Riot really as a whole. Champions aren't their main source of revenue, players are. I want you to think about that for a second. Are champions one of the ways they make money? Sure. There's many other (Including things outside of game) that bring in revenue for Riot. Why was Magma Chamber scraped? Because it would have had Dominion syndrome. Would have been totally awesome for a couple weeks and people would have gone back to Summoners Rift. People play MoBA games for their mechanics and game style, not for their maps. The game is hard enough to balance with the maps we already have. I say continue to fine polish the game we have, make champions that offer new mechanics/play style/team comps, and continue to develope your eSport <---- All of which Riot is doing.
I don't mean to "white knight" or anything, but I honestly believe that Riot is doing one of the best jobs we've seen ever as a game developer.