Modular lenses

Fujifilm recently announced a teleconverter lens for Fuji X100 / X100S that would change the focal length to ~50mm (full frame eqv). I am curious if it would be possible to implement some sort of a modular lens design for such cameras. Put the part of lens involved in autofocus into a camera body, and make the front part detachable. This might reduce the size of camera and converter combos. The only minus I see is a more expensive body. The positive moments: sensor will be sealed, a leaf shutter can be used.