Hi. I think I can help you with TSOF if you'll have issues with triggers. I tried myself out at making various trigger systems. I can also suggest you to make two movement systems: one is WASD when you turn on/off going to left-right forward-back. And ArrowKeys, when you can change angle of attack and rotation. These two separate systems will let you create multiple floors on each level. You can also shake screen on recoil, just use set a variable for vertical rotation to camera's AoA every 0.01 second, then rotate camera according to keys pressed.
I also have a complete Shoot system, which checks whether you shot a cliff, a hill, an obstacle, a somebody or to nowhere. The system consists of a single trigger. But that system is only in my copybook. I'm interested in helping you with FPS, because I'm making one too, I have to make 12 underground levels for it. I am quite disappointed at making underground tunnels and dark laboratories, perhaps maybe you know how to make that?