Relatively straightforward - most of the hardware/casings can be bought off the shelf for 19" rack mounting. I was hoping to find a slimline rackmount kvm console for my rack-bag recording rig, but all the comercially available ones are too deep. Might end up making one at some point, if I can spare the time.
And I have just thought of one potential benefit of a "laptop" that large - you could fit a decent sized wacom tablet next to the keyboard, and provide a stylus and active wacom mouse. Mouse on digitiser pad would probably provide a very accurate input for gaming...