Deep Dark Biome Placement and Compatibility

So I was thinking, since the current caves are pretty cluttered already, I think that the deep dark biome should generate below bedrock. So on the surface there is some sort of indication that one is beneath so you dig down, find a cave system and it goes through the bedrock. Then it is basically a winding never-ending deep dark cave which eventually leads to a massive cave in which the city is placed into.

This would make updating worlds to 1.19 very compatible as they just have to generate below bedrock. Not all the bedrock would change though, just holes in it. 

If you like this idea please upvote!