Suppression effect that includes blured or reduced vision is not realistic or desired in this game, most of the time tracer roudns passing above your head are not going to cause any type of visual hinderance, however I do agree that there should be a supression system.
Most realistic way you can add a suppression system is to use basics of what suppression does in real life, it creates fear, and fear causes increase heart rate. We are talking about battle hardend soldier however but still when your heart is nearly beating out of your mouth you should not have the same capacity to hold your breath or clam your self to place perfectly well aimed shots downrange as when you are relaxed.
simply implemented in game when you are under sustained fire, you should no longer have the same capacity to hold your breath and your aim should be decreased to simulate your heart rate and focus.
it could be as simple as changing accuracy values in stances, i.e:
-if you are being suppressed while standing your accuracy and ability (amountof time) to hold your breath is reduced 25% of current value.
-if suppressed in crouch position your accuracy is changed to normal standing position accuracy.
-if supressed in prone position your accuracy is changed to that of the normal crouch position accuracy.
this is just a simple example/suggestion, I am sure the devs can come up with somthing better yet simple and effective to implement for the full release.