new toggles for World generation (plz read to understand)

my idea is toggleable settings that change world generation for people who don't want a specific biome or people that don't really build could turn off natural generations of blocks they fimd inconvenient

the main idea i have is modes that change the whole gameplay 

such as a spawn in the neither mode

or a sky mode with biomes floating individually 

maybe an underground only mode with open pockets of biomes while the sky limit is blocked off like in the neither and everything is caves

or challenge mode where new obstacles are added so speedrunners haven't more to  do in order today"beat the game" my only idea for this mode is to make the ender Dragon not right next to the spawn in the end so they have to kill a mob in the end to craft a new item to find the ender dragon.

the total point of this idea is to make the idea of playing the game how you like to play more customizable instead of just in game choices