1987 one ton dually, cab and chassis with a CM flatbed installed by previous owner. I'm finally getting around to figuring out the birds nest of wiring modifications. One of the prior owners cut the backup wire behind the cab and spliced in a direct wire to the deck lamp switch. This would allow him to have the back up lights at rear bumper and headache rack come on by the switch. However, this won't pass inspection around here since the backup lights are no longer activated by changing into reverse. I want to keep both functions - normal backup lights (bumper and headache rack) when going reverse, AND ability to switch both sets of back up lights on with the deck lamp switch.

So here's the crazy thought that would allow me to keep things looking stock. Looking at the wiring diagram, it seems like I can do the following:
-replace the deck lamp switch with a 4 runner switch
-terminal 4 wired to the input of the reverse switch (deck light switch is off - reverse switch works as normal)
-terminal 3 spliced to the output of the reverse switch (truck is not in reverse, deck lamp switch is on - lights are on)
-terminal 1 spliced to terminal 3 just to light up the deck lamp switch when on

Thoughts?