I've never tried such a modification but you need to be careful when lowering the nut for this conversion. Lower thicker strings such as the octave strings vibrate much wider and slower which runs the risk for hitting the fingerboard. This is easy enough to solve by scooping the fingerboard until it doesn't touch anymore but if you later try to go back to a normal violin you'll have that greater distance to deal with.
Having said this, we sell nuts and fingerboards.