A camera without an AF motor and no LCD would be the size of the D5300 with the rear LCD removed ...
A D5300 styled FX camera would be cool if you ask me, keep the flippy screen too.
David, I agree the Df is the closest Nikon camera to this concept. My recent musings is a result of going NEF only with my D750 and I was surprised to find how liberating it is to shoot this way, just focusing on taking pictures, and leaving the image processing for on the computer. For me, it's no more work to process a NEF than a JPEG and actually processing NEF's is easier, more features are available in the software. That got me to thinking about a RAW-only camera with a simplified feature set to get the size down, and the controls simplified or like a film camera, Frank's FM-D idea. I agree...this probably won't ever happen, although there is a chance in regards to what Pluton is describing for a mirrorless camera, you never know.
In the meantime...any reason why Nikon would not have produced a D5xx style FX camera? I also can live without the screw-drive for AF...I only use AF-S or AF-P lenses.