I think the best way is to find the wiring for the door ground trigger wire; probably the one from the driver's side door and splice the hot side of the wire to the ground (positive voltage using a multimeter) using a SPDT switch. When the circuit completes to ground it will turn the lights on. When the circuit is closed, lights will be off.
Actually, pretty simple to do really. You just need to locate the wire from the bundle running along underneath the along plastic panel under the door. Once you locate this single wire, you can the cut it and run one wire to the ground to switch (top or bottom or whichever is considered ON), the other two connections to the switch. This is why you need a a SPDT switch. An off position would make the lights work normally just like when you have all the doors close. When you flip the switch, you have a condition similar to when someone opens the the door that turns on all the lights in the interior. I've noticed that not many cars have the central switch for lighting anymore, not sure why. I remember that most cars had this in the 80's and 90's. Even my Honda Pilot don't have this feature.
