I have an old v4 slambox PCB that I'm putting together for a friend. My question is, if I were to omit the LED on the PCB and instead wire it up with the switch, can I just omit it from the PCB without doing anything further? Or would there be some alternate wiring I would have to do? My thinking is that I can just omit it without any problems, I just want to be sure.
You can omit it without any problems. You can safely omit the current-limiting resistor on the board (R5) as well.