Custom Cave Bioms - Better Accessibility for Addon Development

I am currently working on a big addon and one thing that is sadly not possible yet is to create custom cave bioms. My goal, just to mention, is to create a desert underground biome with its own custom blocks, music, mobs and structures. This is only one biome straight from the top of the list that I’d add. I’ve seen some people having made such addons on the marketplace, but there doesn’t seem to be any information available on how to turn those ideas into reality. I hope that you can consider adding something to make the creation of such biomes more accessible for developers. I love the game and I’d absolutely love to be able to create such content for it. Thanks for your time!