I think the breathing key would be a step ahead of most suppression system and would be realistic, since tactical breathing is something you have to take the time to do and is not done automatically when youre in combat, I received a course 3 weeks ago about tactical casualty care, and there was that part about tactical breathing,
there was a chart of the different step of stress,
, and what they taught us, was that you had to frequently stop and assess your combat effectiveness, by stoping and identifying what status you were if youre in the grey area, you had to do the tactical breathing until you were ready to fight because once in the black panic kicks in and that's were some flee from combat or become completly useless
and by the way if anyone is interrested in tactical breathing the idea is : you take a deep breath for 4 sec, than hold it for 4 sec, exhale for 4 sec, and wait 4 sec before restarting the "4sec breathing square"(each step is done in 4 sec) and you do those 4 steps 3 times, and those 3x4steps that is tactical breating, if you want to try it, go run up and down the stairs once or a few jumping jacks would do, take your heartrate, then do the tactical breathing, take your heart rate again, mine droped by 20bpm,
and in combat you would do exactly that take your heart rate and do the tactical breathing until your heartrate is at the desired level