We use perforated aluminum sheet
like this stuff. It's surprisingly strong, and offers plenty of pre-made spots for zipties and other cable management hardware. It's not particularly heavy, either. The one thing I hate about it is that the holes don't line up with component holes, but some precision drilling can make up for that.
Anyway, cool gearboxes. I couldn't tell what you meant by a dropped swerve until I saw the modules in a base.