Transitioning between rifle and pistol and back again is a slow, cumbersome animation that involves slinging the rifle over the character's shoulder. The rifles of modern military forces (not to be assumed all) are equipped with slings that allow its user to "drop" the rifle across the user's torso and quickly transition to a sidearm. Current animation discourages the use of pistols over reloading in close quarters, high intensity moments.
This concept is already put to use in Arma when a character climbs a ladder while holding a rifle, and similarly when a character uses binoculars. The idea of a sling is presented, even if not seen, as the rifle hangs to the side for quick acquisition.
Modern training also incorporates transitioning from rifle to pistol and back again while moving. Currently, a character must stop movement to transition from one to the other. Transitioning should be allowable at least at a walking pace.