It's unique for sure, which isn't a bad thing, but I just can't get over the potential for a fire/one heck of a smoke show. For example, I've been doing a bit of video encoding the past 6 hours and the ol' Q9400 has been throttled at 100 percent for most of that time. It hasn't topped 55C on any of the cores, but metal touching cardboard at that temp would make me paranoid.
No doubt it would make for one heck of a modding PC. You could just keep adding boxes as you add more components. Heck, might as well get a medium sized shipping box, stick 4 hard drives together, glue a RAID controller in there, and declare it the ultimate NAS storage box.