Original keyboard and mouse would be of no use. Is the KB even PS2? Or older? Going to go with a wireless solution for navigation. Will likely add a USB gamepad inside as well for some simple front navigation/playback controls.
Since the entire case is itself basically a large Faraday cage, I'll have to be tricky with placement of wireless bits.
I'm thinking of stealing the AMD processor from my wife's old system. I'll have to see exactly what proc it is, and see if there's a Mini-ITX board that fits it that has decent onboard video output. 90% of the time, I'll be pushing lower end video. Occasionally I'll borrow/rent a Blu-Ray and will want that playback capability. Even an older desktop proc should be more than capable.
Got a slick idea for the metalwork. Once I've got the laser back up and running, I'll start on this idea. Gotta sort out a good way to do it with the tools I have. Might have to fabricate a jig, or rig up something sneaky.