The simplest way to do it would be putting a female - male DB25 connection. A female port on each control panel and a small male port coming in from underneath. That way, when you swap, you just plug it in and play right away.
I am going to use a 40-pin connection because I dont know what Ill do with it. One thing though, in most panels, they mount a panel on a huge box, and the whole box comes out. I dont think this is productive, so I say do the opposite. This way, you will not see a huge mess of wires when you remove a panel.