The Far Lands

While creating a singleplayer world, in the settings where the seed, the name, the bonus chest etc., should have an option "Far lands: true/false", where you would get the option to turn on/off the Far Lands, and maybe if you select it to "On" a number text line would appear: "Blocks from spawn", where when you insert a number in, it would be the number of blocks from spawn where the far lands generate. And if you make it 0, it would make the farlands in the original place (12550800).