There must be other circuits you could use, but yes if you want to use rear lights then using a small relay (and a capacitor and diode because the light circuits are PWM) you might be able to get away with not triggering a warning from the LCM. Does the power draw come from the TCU itself or the fact that it wakes up the car?

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)