No need to make the ACOG into a switchable 1X/4X optic when there is already one in the game. The Elcan SU230 Specter has a big lever on the side that switches it between 1X mode and 4X mode. That lever is even on the model in game, you can see the 1X - 4X markings on the side during weapon animations.
I'm not sure how bad for balance a FTS magnifier would be on any of the red dot sights. The magnifier when flipped off to the side is quite the sight obstruction, even in real life with two eyes and a head that moves. Considering there are already people who prefer iron sights over red-dots because they block less of the screen, having a magnifier blocking the entire lower right quadrant of the screen would be a pretty big downside to that type of sight.