Well, the mod page is here and two weapons have fully functional iron sights! The M4 and the Falcon (the pistol which is based on a Desert Eagle) have iron sights which line up in the center of the screen when you zoom.
These two were the easiest to implement as their models already had functional sight features. The Jackhammer should also be relatively easy to implement, although its sights won't be as precise due to the design of the weapon. The P90 and MP5 both require some sort of modification to the model before they can have proper sighting. The P90's built in reflex sight is not transparent and the MP5's rear sight doesn't have an actual hole in it. Until these problems can be overcome, a crude workaround can be used.
I've been wanting something like this for the game for quite some time, and only recently broke down the last barrier to creating it. An alpha version should be finished inside of this week.
