Just to let you know this is ONLY my opinion.
I think that there should be bullet-proof vests in game for Police, SWAT, FBI and so on but I think that civs or criminals should be allowed to buy them too.
Now I think that there should be more kinds of them like:
Small vests like lightweight ballistic vests, these are its propreties:Can be weared under clothes undetectable perfect for stakeout missions or going undercover. They can stop a small amount handgun bullets and anyone can buy them at any gun store.
Now on the medium ones:Preferd by the police and the FBI they can stop a large amount of handgun bullets and a small amount of rifle and shotgun bullets. The vest is visible and you need a license for it.
The BIG ones:Only SWAT teams have the permission to wear one only in critical conditions and they can stop an unlimited amount of handgun bullets and a large amount of rifle and shotgun bullets.
Also please come with some photos and I want to hear your opinion about them.
And i think you should lose a little health whenever you get shot multiple times like you get a broken rib or something.