Apart from the fact that I just mentioned "yeah, why not make it an Option or a module?", I'm going to make myself very clear: I don't give a flying shit about how this affects PvP. Arma is not a PvP game, CoD is. If you think this will affect PvP negatively, and can't be bothered to actually read what I write, then go play something else than Arma. Arma is a sim, not a shoot 'em up FPS.
Not to mention that, like I wrote, sniper rifles would need either 1 headshot, or two hits to the vest. Now, if you're unlucky enough to hit the vest, the guy will still be knocked over, allowing you to take a follow up shot. And then we're ingoring some obvious things like: You're a sniper, you should be patient enough to wait for a good shot, and body armour works IRL, meaning it bloody well should in a game that is a sim.
And no, buckshot will not spread out so much at 30 yards that a shot aimed at the center of mass will hit beyond the trauma plate. Do you have any idea how big they are? And no, shotguns just can't penetrate trauma plates, that's a bunch of malarkey. Also, yes sure, people might stop using shotguns in some missions. Just like how soldiers don't really use shotguns in a conventional war anymore, because if the enemy has body armour, the weapon will be useless, which is why shotguns are mostly used against insurgents these days, ergo they'd work well in counter insurgency missions in Arma.
For the last time, Arma is a sim, not a PvP game. The fact that there are 60+ votes in favour of realistic body armour and only 7 against means something.
And for the last time, it's being suggested as something that can be enabled/disabled in Options, or enabled via a module. And if that is too complicated, you can always make PvP games without body armour and helmets.