1. Iron-sights - due to the issue of [[ https://community.sogpf.com/threads/499-Which-ironsights-are-difficult-to-use | peep-style ironsights obstructing much of the view ]] in game (as opposed to real life application), it seems to me that current 300m aperture size (bigger one) should be used for both sight settings. Smaller aperture, while more realistic, is just too punishing for the player. Additionally, to "recover" some of the lost field of view, the outer diameter of the sights should be reduced, aiming for the sight-picture similiar to [[ https://upload.wikimedia.org/wikipedia/commons/2/2b/M16_rifle_correct_sight_picture_fig_4-18.png | this diagram ]].
2. Clip-on bipod - it might be worth introducing this accessory, as it was used quite frequently by USMC, as a [[ https://www.flickr.com/photos/13476480@N07/48233692202/in/album-72157718269450193/ | pseudo-light machine gun ]], even until 1980s (introduction of M249 and M16A2).
3. M16A2 lower receiver - this issue is mentioned last, as additional information, because fixing it would require a significant amount of work. Currently both M16 and XM177 use [[ https://community.sogpf.com/attachment.php?attachmentid=190&d=1621526085 | "A2"-style ]] lower receiver, with reinforecements in the rear (where lower mates with upper and stock) and the front (around the front take-down pin). Differences between "A1" and "A2" lower receivers are described in detail on [[ http://pullig.dyndns.org/retroblackrifle/LowerBldGde.html | Retro Black Rifle page ]] (scroll down to "Lower Modification" section).