Sulfite in developer decreases contrast and that is visually same kind of effect as lowering saturation at the same time. Try sodium sulfite at about 0.5 g/l first.
Bleach bypass decreases saturation and increases contrast and density, because silver (monochrome) image is overlapped with dye image. So, use a normal fix instead of RA-4 blix. Or buy your blix from Tetenal . You can also do partial bleaching only. Farmer's reducer works also, reducing the silver image and leaving the dyes.
If you do bleach bypass, you may want to develop for a shorter time to address the contrast and density increase.
You can also bleach-bypass process the negative. However, many color negative films have filter layer and antihalo layer made of silver and you will need long exposures in printing because the ND filter kind of effect.
Experiment! There are many things you can do.