USE OF OPTICS
Developers, if you want players to use all weapon categories, then each weapons category should come with a specific accessory pertinent to that weapon category to make it valuable, unique optics to one particular type of weapons are the best choice to make it possible.
For example, SpecterOS3.4x also known as M145 Machine Gun Optic (only for LMGs). A Custom Sniper Optic 12x magnifications with BORS rangefinder fitted on top with advanced augmented reality visor like Future Soldier (only for .50 caliber sniper rifles). Also, incorporate the NVT scope that combines both night vision and thermal view.