the top image shows the total doc size. the red ruler shows two pages at 1024 x 600px equaling the two page spread of 2048 x 600px or whatever the doc size. Just imagine 2 or more layers just like this.
image 1 and 2 shows the previous doc split equally in two in two different layers. now 1024 x 600px. take a look at the layers icon.
it would be nice to have either a new group folder with the new layers or a new project doc with layers.
the behavior would act like both of these scripts: "export layers to files" and load files into stack", but with splitting the layers in half.
images 3-5 repeats the steps above.