I understand that the point of the hazmat suit is to protect players from radiation. However, if I'm still going to be putting a filter on my face, it should also filter out poison gas. After all, I used filters to make the special filters that make the suit work. Furthermore, the name indicates that it should protect me from gas, as it does not mention radiation, going for the more general 'hazardous materials' moniker.
There is precedent for this suggestion, as the xeno-zapper, the rebar gun, and the rifle all have or will have upgraded versions. Why not the gas mask?
In general, adding a new gadget for every eventuality is not a good idea. It can lead to confused and disgruntled players. For example, imagine if the player had to craft, use, and keep track of a separate ore scanner for each ore. That would get pretty old, pretty quick. Instead, you have one gadget to scan for every type of ore, and that makes the game much more intuitive. If you were to present the suit as an upgraded gas mask, it would make sense, and reduce inventory clutter.