careful with that all. Not everyone uses there computer for the same reasons, some people need certain features, more or less power, limited space or a lot of space, and so on. Some people even have many displays which need to be ran like independent computers on one computer which obviously this would require more graphics cards or maybe even just one graphics card with eye infinity.
There are various industrial motherboards, in mini-itx, 5.25" and 3.5" form-factors supporting mobile chipsets and cpus - I have been advocating for a long time to use these in carputer environment.

They are significantly more expensive, and signficantly more stable in these harsh environments.

Look at Commell/Advantech/Kontron/BCM and many others for examples. Mine works perfect everytime. Never missed a beat, and I can drive multiple displays, most will even have LVDS ports onboard to directly interface to openframe LCDs, without separate controllers....

So, it's a brilliant idea - again, for some like Hijack, these won't work.....due to the complexity of his setup.....but for 99% they would.