being able to make a custom seed for creative players

I would like to see a feature for creative mode where you can basically paint biomes how you'd want them to be located in the world, and have Minecraft input that into the seed generation and fill in empty spaces to make a custom seed that is still generated the way Minecraft would. Like world painter but actually implemented into the game as a feature. Like I could paint I want spawn as one biome, and these other biomes this far away, and Minecraft will fill in empty spaces the same way it would generate a new random seed