If you could keep the lens stationary and change focus by moving the camera then it would be great. I have seen a thread at: photomacrography.net/forum/viewtopic.php?t=4879 where the author describes just such a setup.

My analysis of the two situations:
1) Move the camera and lens together without changing the distance between the lens and camera (no focus ring change)
2) Change focus using the lens focus ring - move the lens with respect to the sensor/film position

In 1) the optical characteristics of the lens ...

Moving the camera is preferable because the focal length of a complicated optical system such as modern composite lenses (made with several elements) does not remain the same when focus shifts. Moving the camera with its lens assures the same optical performance for every shot in the stack.
Be sure ...