I have 0 experience .. just read a lot of things .. i thought that being hit by a bullet varies a hell of a lot in terms of how you end up after being hit. You are probably right about most of what you write, but i have read that it depends a lot on the angle of how the bullet hits, and as you mention, the velocity and caliber. All of these are things that JA3 can implement to a greater degree than JA2 had, even if that was good as it was.
In real life, i imagine that it is so much down to random. Even a stray pistol bullet that hits an artery can mean death, and even an aimed sniper bullet that just misses an artery means someone lives. Of course protective gear would play into this. But i also think that implementing too much of this into a game, means it becomes so much to take into account that it may take a lot of fun out of the game. That would be a delicate balance. Spending a lot of time preparing for a battle, making super slow and steaady progress, and then have 1-2 mercs killed on very small odds shots by the enemy. That would feel very unrewarding. That could happen in JA2 as well, but if you played the game right, it could be something you could accept and advance with the game, because again, if you planned and approached the battle ground correctly, that didn't happen often. So that is a perfect blend of realism and fiction. That is where the JA games has something unique. I guess it's an overall balance thing - you can't expect a gamer to spend a whole year to finish a game. I can finish JA2 on expert, iron man in about 60 in-game days, and estimated, about 150 gaming hours, playing conventionally. I feel that is very balanced.
Back to the point: Most of the time, in JA2, what happened was mercs getting hit in the shoulder or head and losing dexterity or wisdom points. Which i found somewhat in line with realism. This area could be developed.
Lol, making a long post here but i have a lot of thoughts about this game since it is so great... One thing i felt could be improved on the point system in JA2, was that, if you didn't use a skill, trait or expertise over a certain period of time, it could start to deteriorate. Meaning it would be beneficial to keep certain experts on a team and keep them in practice. In JA2, i would make it a point, at least at a certain point in the game, to have everyone equipped with repair and med kits and have everyone take part in routine activity. This would increase their dexterity and wisdom too. I don't quite know if this would make a huge difference... but it is more in line with real life. The nature of the mission length in JA2, probably doesn't make this a huge issue, because it usually takes weeks or months to start forgetting innate skills one knows a lot about, or has practiced a lot. And at least in JA2, the mission lasts at the most 3-4 months. But it would be a realistic feature.