From what I can tell, there are varying degrees of wound. If you get hit by a .308, the blackouts seem to be fewer and having a longer interval between them. Where, if you get wounded from a 20mm, the blackouts are more frequent and you get less time to live.
Getting a total blackout for every wound is rather simplistic though. IMO, wounds should have different effects (such as slower response on controls, unable to turn head to look over shoulder, tunnel-vision, but not total blackout, etc.)
What would be really cool (some might say gamey) is a clip-board page that shows the pilot body (front, back, side like a doctor's chart) and where the wound is with red dot. The larger the dot, the worse the wound.