Separate mob cap below y=0

The 2 major ways to spawn proof an area for a mob farm in Minecraft are 1) Digging a perimeter, and 2) Lighting up every cave in an area. Since bedrock is 64 blocks lower in the 1.17 world generation, that would result in an extra 64 blocks of space that would need to be excavated or lit up. The simplest solution that would keep technical players happy without demanding extra labor is to simply have a separate mob cap below y=0. This way, players would only have to excavate down to y=0 when building perimeters to have a maximum efficiency mob farm.