I'm too tired to try and figure out if this would work, but initial impression is that you're adding a relay in order to get the fog lights to come on only when the headlights are on (either high or low)?
Also you realize what it takes to get at that wire (Body ECU 13) right? Basically means removing the Body ECU from the dash which isn't easy or quick. I did it for
my DRL Toggle Mod. Honestly you'd get it done more quickly and simpler with Antman's Mod, plus be able to run with out headlights. Besides do you really need the fog light LED on the dash if you can see/feel the switch? When you can't see/feel the switch easily, it's probably dark enough that you'll see the fog lights!