You’d have that anyway. It’s either going to be a long tunnel or an escalator. The amount of underground land off limits there do to various train lines and platforms is insane.

It would be like the passageway between 42nd street. A long crowded walk.

You’d also have to deal with modern safety standards. There’s not nearly enough exists on that thing by today’s standards. So you’d need to find ways for at least some emergency exists, build and buy some land for all that.

Still complicated, still expensive, not making things faster.