in my opinion the single greatest way to improve player immersion and their experience in your game, is your sound system, its good, and with additions such as ricochet sounds, reverb for gunfire indoors to simulate pressure and just more dynamic noises in the environments, as well as basic environment interaction such as chunks of the wall falling on the ground, then your core gameplay loop which is centered around your weapon handling systems will have that much more gravity and satisfaction. But all in all AWESOME GAME KEEP IT UP!!!!!