I'm almost certain someone once posted pics of their breeding pens that were constructed with modular walls dividing it into 4 sections. The walls were removable so that, when desired, the space could be converted back to one large open area or a medium-sized area with one or two smaller areas.
It seemed a very space and cost efficient design. The exterior of the full space was predator proofed very well and the modular walls were lightweight chicken wire as they only needed to keep the birds separate. They were solid for the bottom 2-3 feet though, to prevent the roosters in adjacent pens from seeing each other. It was quite ingenious, IMO.
Do you have the link to where it was at?