When will custom biomes for Bedrock Add-Ons be fully implemented?

Just a heads-up: I'm a Chinese player, and this text is translated by AI. I'm not sure if I can get my point across perfectly to you.I don’t really know how to phrase things in English properly, so sorry if this sounds a bit off!Basically, I'd like to make a biome based on the "Garden" from Deltarune Chapter 5 in Minecraft. But it seems like the only option available right now is to replace an existing biome, rather than creating a completely new one.

I'm not very good at coding, so I tried replacing the plains biome. But the result is that the biomes appear in patches, and it feels like every plains area has some part of my "Garden" biome mixed in — which isn't what I wanted.

What I actually want is for the Garden to be an independent biome that spawns less frequently, but in much larger and more continuous areas. With the current replacement system, even a small patch of plains would inevitably get covered by the Garden biome.

Also, it doesn't seem like I can change village spawning rules. But I'm planning to add a new type of tree to this biome, and if villages still generate there, it would look really out of place and break the atmosphere.That's why I truly hope you could consider fully implementing this feature.