-Ability to shoot from inside of a vehicle.
-Improved AI much, much work here + add animation when you can surprise enemy maybe just little shock and sometime fall.
-Gore, decapitations, etc (not necessarily but can add to immersion).
-Better blood after hitting.
-option to change bobing in FPP ?
-Dust clouds could include little stones and gravel.
-explosion should overturn the gamer and let him get up (but can be exploited I' not sure about that)
-IED
-weapons malfunctions
-particle effect with explosion (ground, parts of vehicle, etc)