High side P channel MOSFET power switch - gate question, and suggestions for my circuit?
That LED being in the emitter - to - ground connection of Q3A is going to give you some grief since you've only got 3.3V (less actually because of the R7 R8 voltage divider on Q3A's base) to drive Q3A with.

Fix it by connecting  Q3A emitter directly to ground, lose R8 and drive the base through R7, and connect the LED from the source of Q1 to ground through a suitable ballast resistor.

From your question:

"OUTPUT4 is the high power load output, which is connected to the Battery negative terminal through the system's common ground." might be better worded to indicate that one end of the load - not Q1's source - will be connected to battery minus.