The game is complex and this is good but there comes a point where "realism" becomes simply "hassle" to deal with and ruins the immersion.
For example:
There is no need for fully half the commands currently in game listed on the controls setting page, these should be combined and integrated into other commands like ever other FPS game does.
In my opinion the spirit of the game is to provide a fun and enjoyable sandbox where one can get into the action and enjoy it, rather then having to think about which of the 168 keys he needs to press to elevate his gun 2 degrees, and then spending the next 10 minuets trying to fix his weapon back so that it fires correctly.
If you are using more then 20 Keys to control anything (honestly id say 10 is plenty enough for an FPS) (without some streamlined option) Controlling your character then becomes a hassle rather then second nature.
There are only so many things which are key in an FPS:
Movement - wasd, Mouse (Sometimes q and e for strafing), Crouch, Prone (should be the same button that cycles)
Firing - Mouse button, zooming/look - Mouse button 2, changing weapon - scroll, Grenades (Keyboard button and maybe an additional one to change grenade type).
Specials - Infrared etc, Bipod,
All in all the above is less the 15 buttons. There is no need to have 60 commands for movement, 30 something for weapons, etc. These commands need to be streamlined and combined as I said above to make the game less clunky and easier to play.