Looks awesome!
Not sure where the fans and motherboard are in relation to the USB panel and the chair. Close enough for easy thumb drive access without poking the user.
It looks like the back of the motherboard (where the power/video/network ports are) is against a wooden part of the frame? Maybe there's more space than appears.
You might be looking at the workbench? It will be an aluminum panel similar to the rest.
Where are you putting hard drives? Between mobo and fans?

Is that opening on the top to access for plugs/setup?
That will be a hidden-ish compartment for whatever
It looks like fans are hard mounted to aluminum hard mounted to 8020 with a great big sounding board (desk top). That could cause vibration noise, rubber mounts or slow fans or both could help.
The fans are rubber mounted
Same vibration thought for hard drives.
Good call, i will need to isolate those as well
If those fans are pushing in, a filter might be a good idea. Maybe being off the floor helps, depending on how clean the room is. Some kind of guard against fingers seems necessary, unless it's going against a wall, and then you need to leave room for it to move air.
I plan on having a slide out filter somewhere. The idea is to make a slide out cartridge and cut up HVAC filters to use.
Those fans pushing out with a big slow fan hidden somewhere else, maybe under a hdd rack, with a big filter could be helpful.
If you're doing a wireless mouse/keyboard, my logitech unifying receiver doesn't like being under my 1.5in thick wood desktop. Bluetooth for headphones suffers less, but if you can get those dongles in line of site to the device it helps. Again with the extension cables.
Good to know. I will keep this in mind!
If there's room in there for a network switch, I love having one drop to my desk in the wall, and then ports available for server/desktop/laptop/printer. Yes wifi is great, but that computer isn't moving, and wired will be more reliable, especially in a metal box.
On the checklist
While you're printing panels, you might also fit a temperature display somewhere. I imagine you'll hear the fans spool up, but flight sim and solid works can be intense.
I have a fan controller with probe getting mounted in the second cutout by USB hub
Maybe build in a wireless charger pad?
I completely forgot to order this. Thanks!
Build in speakers?
Those will be wall mounted.
Ram mounts for tablet/phone, headphone racks, tray to store keyboard and mouse if you do paper drafting at the same desk?
I am debating a swing out tray from one of the panels.
I'm looking forward to seeing the final setup!