Actually, if you think about it, peripheral vision is already modelled in the game.
You see, since we are limited to these small, X inch by Y inch area of monitor space, the default plane cockpit we see in the game is typically set at a "panoramic, wide-view" position.
In reality, if you use the zoom keys and max-zoom at a target in AH2, that's usually the actual size of the real gunsights in real cockpits. But ofcourse, if we fly around in that zoomed-up view, we don't have any peripheral vision at all.
So, inorder to expand the visibility, the default cockpit we have is shrinked up. The 'border areas' of the monitors are where the 'peripheral vision' would be, except it's not blurred up.
The problem is, "blurring up" those border areas are neither much suitable for gameplay nor realistic. It may "look" realistic, but actually our default game screen is much more realistic.