As a combat vet, US Marine Rifleman, I say add this feature; HOWEVER cut the accuracy in half when shooting this way. I mean think about it... the NVGs stick out about 5 inches (2.5 cm) in front of your eye, and you have to line them up perfectly in order to see through the scope or iron sights. This is extremely cumbersome and puts you into a very uncomfortable/unnatural shooting position. But, it is possible and sometimes useful. Sometimes the ability to see clearly outweighs the ability to shoot accuracy. Sometimes it's the other other way around.
With NVGs on, we're trained to look down the side or top of the rifle. We simply line the target up with our rifle rather than looking through the sights (like what is already possible in the game). As for mounting the NVGs onto the rifle, I have very little experience with this; but I do know it requires a special attachment/mount (or lots of tape).