If we make it so that this part is only targeted towards a specific toxin so that modification makes it targeted towards one at a time only, balancing can be a lot better than a simple “put-down-and-forget” part with general resistance. That way, players will have to remain aware of the type of toxins in the environment, and will have to judge whether or not stacking expensive parts is worth it.
Does hydrogen sulfide react negatively to oxygen? On Earth, our oceans became much less sulfuric as oxygen began to reproduce, relegating sulfur-dependent metabolisms to more geologically-active or anoxygenic environments. So even if sulfur does spread throughout patches, the presence of oxygen would make sulfur deteriorate like iron as well.
I think that’s fair. If we get enough positive reception to that option, we could just tweak the starting presets at some point during Multicellular development.