Soldato
Hmmm, yes you can. The internals themselves really don't take up much room at all, it just comes down to the prism size and sensor size. Most stuff outside of that doesn't really matter and size just comes down to what customers want at each price point. You could put a full frame sensor in 1100D or D3200 sized bodies if you wanted as they all have full frame sized mounts, which is the main size determinant of bodies.
Have you actually seen how big the EOS-M cameras are? Canon shot itself in the foot with them already as they are massive compared to the other compacts as canon has tried to turn it into a 650D with a slightly smaller body. Hardly gonna fit in your pocket is it? Utterly pointless product imo, especially when you compare it to a nikon V1 for example.