A Way to Increase World Depth in Old Worlds

First, I am defining world depth as ocean level to bedrock. Their are people who think to the depth of world should/will be increased in the Caves and Cliffs update (myself being part of the former). If this were to happen there would be some difficulties in getting world world to change in depth. My idea for an option on (I think there should be deferent way to do this that the player gets to chose if Mojang were to implement a depth increas ) how to solve this to for the new mountains to generate on the start of pre-1.17 chucks and act as a barrier to make the transition less noticeable. This would also serve as a way to show off the new mountains.