[MENTION=145718]rypajo[/MENTION] agree, way more involved than I cared to do.
Posted the question on Reddit and received this response:
[–]MyNameIsRay 1 point 2 hours ago
I'm guessing you want a single three way switch that controls it all. Middle off, up is "on with domelight" (whether that means off, on with doors, or always on), while down means "always on no matter what domelights do"
Get a relay. 40a 12v 5 pin, as is standard. Pin 85 to chassis ground, pin 30 to +12v power with a fuse. Pin 87 is +12v to the lights, lights will use chassis ground (ring terminal to metal, for example).
Now for the important part:
Pin 86 goes to a the middle pin of a 3-way switch like this one (3 terminals is the part that matters, not the shape/size/design/color).
Top pin is tapped into the +12v line of the dome light, use the instructions you posted to find that. Bottom pin goes to either +12v ignition or +12v constant (depending on whether you want these lights to stay on with the key off or not).
Once wired, when the switch is in the middle "neutral" position, the exterior lights will stay off no matter what. When the switch is up, the exterior lights will do whatever the dome lights do (On, off, or on with door). When the switch is down, the exterior lights will always be on regardless of what the domelights do. If you tap ignition, they'll turn off with the key. If you tap constant, they'll stay on even without a key.
This seems a little more straightforward. I only have to hunt down one wire and the rest is independent.