A to-scale would use a lot of plastic and it isn't that cheap. That, and the Pi doesn't need that much room to begin with. The most scaling I've done is for the length, as it would just be empty space. I've left enough room inside for cables and a tiny fan, as the little Samsung System-on-a-chip generates a fair bit of heat.
When I print the new rear panel I'll probably add some tiny vents. The current one was originally intended for a DE-9 carrying a combo of A/V signals, but I ditched the idea in favor of using a single HDMI cord.
And yes, the printer is limited to a size of 1' by 1', IIRC.
This is actually one of the first projects I'd considered. Unfortunately there aren't any translucent plastics for this printer, it's a bit old.