Yeah, I'd agree, moving the whole electronics panel above the toughboxes would be a good step.
Here's what I'm thinking:
Instead of the small angle bracket attaching the toughboxes to the top panel, attach the tops of the toughboxes to the side panels with standoffs or long bolts through some spacers.
Stick to a simple electronics board. PDB, Talons, Router, Arduino, Breaker, all of it, that sits just above the toughboxes. Hold it down with a couple of wingnuts or some other easy-detach method.
Get some standard 120mm PC case fans, and mount one right under each CIM (obviously this will require holes in the bottom panel too
)