It would be cool to design custom aluminum brackets for the fans. However I found that although ordering 3D prints is very cheap, using (for example) PCBWay for CNCing something out of aluminum is very expensive.

Why use the original power bricks, with the space claim and awful routing, instead of just going to a single dc/dc... either directly if no individual power control is needed, or to a relay block or switch block if automated / manual individual control is needed?

Awww, its so adorable

This looks good: I've got three HP NUCs like in TFA + three Pi on my desk (got more than that altogether) and it's indeed a cable mess.

> Aluminium extrusions are bars with a groove on all four sides. These bars have a standard format and you can slide all kinds of equipment in there and lock it in place with set screws. It seems to be used a lot for home made 3D printers, CNC machines and whatnot.

They're also called "T-slot" and 80/20 (from the brand).

https://en.wikipedia.org/wiki/T-slot_structural_framing

Plenty of free 3D models for tiny parts for those that can be printed at home (careful though: most won't hold much weight).