Well my tentative plan is to duplicate the functionality of the
individual boards, but not to scale. Many DEC machines of that era
were built with "Flip Chip" boards, 2.5"x5" PCBs with card-edge
connectors that typically implement relatively little logic...say, a
pair of flip-flops.
When I was a kid, my dad got me some time on a tanker (ship) that was
being automated. They had a fridge-sized console that was built that
way which ran things. I spent a few days helping them finish the
install and teaching them electronics, and they let me ride with them
on the sea trials.