Why exactly do you need a fan ? These bikes were designed to run without them. Has there ever been reports of overheating and destroying the engine ? The GS is sold in desert states like Nevada and California and I'm pretty sure if there was a threat of overheating BMW would have put one in as standard.
Ha ha ha just kidding , they can be pretty stupid sometimes. But I'd like to hear feedback of one person who suffered a failure from overheating.