there was a hub made with it before, why not just put the whole PC in it? I'm a minimalist by preference so the external keyboard could be one of those fold-up PDA keyboards not unlike the xbox 360/PS3 keyboards that attaches to the controllers.
This one for example.
The video card could output to DVI/HDMI so it can hook up to a monitor or Hi-Def TV. Power on the PC by pressing a corner somewhere. If ventilation is a problem, make it so the design on the allspark is the ventilation itself (Fan inside of course). Have your basic, memory, laptop component Harddrive, external PSU, and Slim-factor DVD/Bluray drive that comes out when you press a corner on the Allspark. Add a Logitech wireless/Bluetooth mouse and you're set!
just a thought ^_^