I don't see any problem with using a relay to power one side, much better than jumpering both sides together and doubling the load on the LCM driver and wiring. Might produce some codes but should be functional till you replace the LCM like you said.

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