Hmm... after looking at it again, I think you're right. It would indeed fit into one box, which could be made out of metal. It would be a bit of a heavy one, but certainly better feeling and looking than the plastic one.
There's probably just two tricky things that need to be checked: how do the buttons stay in place, and how to make the LEDs around the big rec buttons shine through.
From this picture here http://medias.audiofanzine.com/images/normal/boss-rc-505-loop-station-1233487.jpg it looks like all the controls are on a PCB that can be panel mounted.