The GFCI will protect the lower switch/outlets from ground faults, etc. Not sure what you mean by overkill on this. The single point of failure is that if the GFCI trips, everything will shut off. If you are thinking I missed something, please explain. I don't want to overlook things while I am still building it out. It is easier to make changes now than later.
Biscuit, thanks for the kind words. I am glad that I was able to help, or at least I think I helped.
As far as the GFCI, I was talking about overkill on my setup not yours. I used two GFCI outlet (and a covered outlet) where you only used one. My thought was this. If water got on something, only one receptacle would trip. Therefore, my lights (two of the receptacles because of multiple timers) are on their own GFCI outlets. If they get wet, the lights go off, big deal. For the pump and heater, they are on their own outlet with a protective splash guard over it. Inside this is a switch so I can turn the pump on and off for water changes and a constant for the heater.
So wow that is confusing without a picture. I will try to post one tonight. Basically all I was saying is that with a single GFCI, if it trips, everything goes down. I added a secondary precaution to keep my pump and heater going. Thoughts on this?