add and re-work some of the Marauders/players audio cues.
ADD:
Add coughing audio when your health bar is orange or red, with a smooth ending audio file for when you heal back up. (ending audio could be a deep breath or some kind of relief sound)
RE-WORK:
tweak the grunting audio and the out-of-breath audio (or really all the marauders audio cues other that voicelines), to make it sound like their really breathing through a gas mask. For example like when there is a minute left in raid and your guy starts gasping for air, you can hear his mask.
WHY:
This would bring more of an immersive feel to the game, it would also make more people push in fights/bring slightly different tactics, and it's probably more realistic for your marauders to at least complain when he's been shot 3 times.