As stated above, sulfite has a complex functionality in developers, especially in metol based developers. In D-23 it acts as a silver solvent, preservative, and alkali to raise the pH to a point where metol will work. Just eliminating it will not work. Gainer did a number of experiments with eliminating sulfite from developers. They are almost all documented in the APUG archive. He used ascorbate as a combination developing agent and preservative (anti-oxident in this case). They all required a fairly strong alkali to make them work. Most of these developers were not terribly successful, although they were interesting.
Sulfite-free developers from Patrick Gainer