...According to battlefield

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I don't want to be offensive, but adding smilies to a feature request will decrease the chance of upvotes.

Why do you think, that a foregrip will give your rifle a better stabilization?

Don't foregrips, in a way, decrease recoil because your "pulling down" the weapon, and gravity is also forcing it down...
Something like that...

Foregrips aiding the maneuverability of firearms, because you will get a more comfortable holding position for your off hand (holding hand) but nothing more.

Yes bipods are being added but why do you want foregrip-attachments? You are already grabbing the rifles with your other arm. It won't really introduce anything new to the game.

Because it will add more variety to the game?

There's a point when variety is just there for the sake of variety, and this is that point.
In real life, you wouldn't pick a certain fore grip over another because it "decreases vertical recoil" more. It just doesn't, that's not how they work. It's all in how you handle your weapon. You'd use what you're most comfortable with and what makes you shoot best. This is different for everyone, but the end result is generally the same across the board: a good shooter, as good as you can be.
The best and simplest way to portray this in Arma is to not portray it. It'll just be an unnecessary complication to an already complex game with nothing to show for it.