That is in many ways the goal. It's a question of "which level of the protocol will control the lists of communities and, in turn, create nested lists of them."

As of now, one can create an application that nests NIP-51 lists. I believe there is value in doing so, but it's a question of how it benefits the application, or a question of what application you are trying to build (with nested lists).

I envision giving users the ability to create nested lists of communities that can scale to become national or global communities. It's a question of how, though.