Add Custom Game rules?

I don't know if its ever been recommended on the Boards before, though it probably has lots of times, but Riot should add lots of rules to change like Overwatch. Like be able to reduce or increase Cooldown times, ban certain champions, make duplicate champions allowed, etc. I know Riot has thought about it, and I'm wondering why they don't implement it into the game. Yeah, people can recreate urf and other rotating gamemodes, but whats so bad about that. Like really. I want a Real and Good reason why that is a bad thing. When is it a good idea to limit a certain gamemode to once or twice a year? When is it a good business plan to give players their favorite gamemode once every other month, when you can simply make all the gamemodes open permanently. Even if Riot doesn't do something like that, why not at least give players the option of using any rotating gamemode in Custom Games? There's no real reason to let their playeres to only play One For All once every 2 or 3 months.