Removable Bedrock

In order to allow for new generation below existing worlds in the coming 1.17 update, and to allow for players more control over landscaping near the bottom of the world, I would suggest that bedrock be removable in survival— above the lowest level. 

This would leave a 1 block thick layer of bedrock above the void that cannot be removed. Essentially, the bedrock becomes two different types, or else takes on two distinct property types based on its location: a removable kind and an impenetrable kind.

The best way I can think of achieving this is making it breakable. It would not drop anything, ever, even when mined with silk touch. An unenchanted netherite pickaxe would be a bare minimum to achieve any damage, or maybe it even requires a special enchantment. But bedrock would damage even netherite ridiculously quickly regardless and take a long time to break, maybe like mining obsidian with an iron or unenchanted diamond pickaxe.

Bedrock should still have its essentially infinite blast resistance.

This would allow players to keep the lowest levels of their world tidy, for those who operate at that height. But more importantly, it would be an interesting prospect we haven't seen in any other updates, where players need to travel to unexplored chunks to access new generation. This way new generation could be created and accessed relatively easily below existing worlds, which would be super cool!