have you thought about trying to emulate the signal telling the ecu that the a/c is running? I have absolutely no idea if this will work, but i do notice that without a/c i idle at 650-700 rpm, and when i switch the a/c on it idles at 850-1000 rpm. So would it be possible to tell the ecu that the a/c is running without it on so it runs the engine higher?
or tap a line onto the rheostat then to a switch so that only when the lights are on will the switch activate and tell the engine to idle higher, granted I have no idea where you'd hook that up ono the ecu, you're the programmer not me.
I'm just spit balling here.