Gamerules In Menu

It would be really useful for map makers and all kind of other players if we could optimize gamerules while creating a world.

On the world creation menu,there should be an option title for gamerules.That way we could set the gamerules with toggle buttons or numbers before the world is generated, which is a lot simpler and easier than doing it in-game, and getting rid of the affects that the gamerules we changed has done to the world before (e.g.: killing already spawned mobs after setting doMobSpawning false).

This idea could also be in the world editing menu,if it works with the world generation menu.