Customizing the Top/Bottom Bedrock separately

[zephiii]

Pretty much what it says on the tin. In short, you draw a line at sea level, and any bedrock above it becomes the "Top" block while the remaining bedrock becomes the "Bottom" block.

I'm pretty sure someone's suggested something similar regarding forcing a bedrock floor before, but this talks about modifying them separately, so you could have:

• Overworld (Vanilla): Air Top, Deepslate Bottom
• Otherside (Deeper & Darker): Deepslate Top, Netherrack Bottom
• Nether (Vanilla): Netherrack Top, Bedrock Bottom

Instead of just having Bedrock at the bottom.