Custom Sky-boxes for each biome/dimension

It would be really nice for mapmaking if we could have sky-boxes. The only way to use them in Minecraft is either with mods (such as Optifine) or to use the End sky-box (which isn't too useful due to the same texture appearing on all sides).

I think we should make it so that we can add custom sky-boxes to Vanilla Minecraft using texture-packs, similar to how Optifine does it. However, unlike Optifine, the sky-box should be dependant on the biome the player is in (for example: a mountains sky-box texture could only appear in an Extreme-hills biome, while every other biome has a vanilla sky); or we could have it for each dimension instead, and add the ability to create new dimensions using datapacks (The mountains sky-box, for example, would only appear in a custom dimension). This would be really nice for mapmaking because you can have multiple sky-boxes while using only one texture-pack.