Just a few days ago, someone posted pictures of a truly filthy interior of a desktop PC, and it was pointed out that there are two advances in technology that have lagged since the very first IBM PC.
The two are connected, because they both exist because of the same problem: cabinet heat. Because of cabinet heat, desktops use “gawky” and primitive electronic boards, instead of sealed cases, and use fans that expel hot air away from hot components. Which bring in copious amounts of dust.
If you can overcome the problem of cabinet heat, the entire computer could be modular and tidy and assembled in just a few minutes.
It would seem that the way to do this would be for the computer cabinet to be sealed, so no new external air and dust is introduced, and the ambient air temperature inside the box is low, even cold. In turn, cabinets would be vacuum insulated, to keep the inside cold.
Fans would still be used, but smaller fans on each module that generated heat.
Initially, when the computer was turned on, the heat exchanger would take a minute to cool down the ambient air. In turn, an external heat sink would get hot for a bit. But during normal use, the external heat sink would be a little warm, just exchanging heat as it was generated inside the box, warming the air that was then cooled.
HEY! Who's been messing with my pc?
I'm guilty of baaaaaaad maintenance (slapping myself).
Everything you suggested is available now for industrial system on a chip PCs, sealed cases with peltier exchanges, the cases themselves milled aluminum with 5 sides having radiator fins, external power supply, SSD, etc.
The system costs about $3000 for a single core pentium though.