Its an interesting idea... but afaik, virtual pinball tables take a lot of horsepower to run well without skipping frames, delays..etc. As can be seen in the video, the ball pretty much vanishing at times. That would be very frustrating to me.
I think a small form factor motherboard with desktop cpu (not reduced mobile cpus) would be the better workhorse solution internally.
Also, LCDs bulbs have a lifespan. So maybe better to use brand new LCDs rather than a used laptop, which could expire in a short time... thus having to rebuild the thing / repair the backlight.