I was really thinking that we could work on a 1 point damage from weapon equals about one point per minute bleeding damage (for every point over about 3 or 4, to discount shallow wounds where the bleeding would stop itself momentarily). Depending on how someone figures out how to code it, we might be able to adjust that slightly with different weapons (say, sharp weapons 1 point for 1, non-sharp weapons somewhat less, maybe .7 or .

. That's a shot-in-the-dark estimate ... it might actually come out 1 point per 2 minutes, or whatever.
Then, adjust the weapon damage to follow ... current RCM numbers were set up to include the possibility of rapid debilitation from massive blood loss, so many of those numbers would have to be lowered. That would have to be done manually, i.e. by me, and while I'm looking at a stack of medical texts and FBI police shooting reports.
This would result in a model where any moderate to severe injury would result in combat casualty within a few minutes. That is, you take an arrow in the gut, and the time you can fight like that is not very long. However, it would not necessarily result in going down immediately either ... especially a particularly tough person could probably still inflict some damage after taking such a wound, at least for a few seconds.
This would have nothing to do with head shots, really ... since a head wound that is not debilitating still bleeds, and that really does not change the probability of a head wound being immediately debilitating (either from direct weapon trauma to the brain or spine, concussion from indirect shock, or the massive pain and psychological shock of face and eye injuries. Neck hits, which are prone to cause massive bleeding as well as nerve damage and trauma to airway, would respond about right to the data as well.
Since the damage inflicted is already a chance roll within a given parameter, a second probability roll is not really necessary. More damage equals more bleeding, damage times set constant equals blood loss.
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But all of this is pure conjecture until somebody constructs an efficient way to collect weapon hit data without having to run health checks on every unit every second. Otherwise, for programming reasons, this would create such a lag on the system that nothing but the most over-simplified mods could run. (Repeated health checks might work in an arena, where battles were always less than 10 guys, or if used only on the player like KON_Air was doing, but not on 70 troops.) So in a word, the exact formula is on hold until the code is in place ... and I can't do the code, that's for sure. Not anything that will ever run that efficiently. Somebody (or probably several people, before it's done) is going to have to have a real stroke of genius to think of a way to do that.