sounds like you have a good idea of how to approach this... belkin has a kvm switcher that also switches usb that is perfect for multi screen control... they are compact vga switchers with remote controlled wired clickers that are easy to replace with alternate controls, the nice thing about them is if you use them with touchscreens as you switch screens you can also switch touchscreens simultaniously through the usb switcher built in.... pick up a few & play with them, an array of these can control & have available on any screen: pc1out1,pc1out2,pc2out1,pc2out2...,
also, you can use a network storage enclolosure for your media drives to make them accessable to any station.. add a kr1 router or equivelent for total network & mobile hotspot use... I don't know how much space you have to work with, but laptop boards can be an option, 2 pc's can take the space of one more conventional pc, villagetronic vtbooks are great for multi screen on laptop boards...
I have a multi pc networked install that I'm doing right now in one of my cars..., good luck with it
