What to put on your weapon? My opinion is out of date and not as exciting as looking through the latest catalog of goodies.
1. Be the first to hit a target at close range. Once your reflexes tell you to shoot NOW, you will need to have the fastest thought process to get off the shot. anything more than aquire the target as your safty goes off and pull (a very fast controlled squize) the trigger will slow the time it takes.
If this includes running through your mind the options that you may have had. like pushing the little button for the light, or how about the switch roe the lazier . Maybe you have optics, if they have a piggyback dot sight. then add to the option as to which optic to use. the list can go on and on. If you have this equipment on your rifle you will spend time learning exactly were the controls are.
If your mind even spends a nano second on options while the enemy is just a few feet away with his third world ak that has no options to consider, you may come in 2nd place.
2. Reliability, carring your rifle to the local range in a protective bag, shooting it a bit and carring it home is not much of a reliability test. I carried a m-14 in Vietnam, it was teriffic, However during the monsoon it would apear to grow green stuff in less than a day, and during dry hot times it grew sand. I cleaned it constantly, not just daily. I always had a tooth brush and rod with me.l Any equipment that you add will probably not be as reliable as your already suspect m16/m4 is.
3. lights, My training in the Marine corps about lights in the 1960's was, never use one and when the enemy turned one on, shoot him.
Now above all remember that I am about 20 years obsolete. Keep what I said in mind and learn from the new pros. Then you will know what to do.