I need to look back for Mneary's dark sensor, missed that.
Get a book like the Forrest Mims mini notebook series,
this one has basic ttl, cmos, transistor, opa/comparator, etc. logic explanations in it. Also there are some simple example circuits to build for each type.
If you have an extra comparator and ldr (or photodiode) laying around then breadboard the Dark Sensor circuit,
less the transistors and relay stuff. Have the comparator output light an led for confirmation of the dark state. Now you are ready to OR the output of the Dark sensor to say the East (U2A/D or U2B/C?) output. Please refer to the LM339 data sheet for OR'ing outputs, it is very simple and clear.
I am thinking that the East output and the output of the Dark Sensor should have 1n4148 diodes so as to not interfere with each other, comments?. Also, how about putting NC limit switches "inline" with the circuits output to the Nfets, as opposed to grounding the outputs? Guessing it depends on best practice, or which type of switches you have (i.e. NC or NO).
Whatever works, and defer to others as to the best path. For the moment, I am following a parallel but slightly different approach.