It can be done. The Fan Delete Mod seems common in some circles. But you cannot simply remove the viscous fan and coupling only. You also need to replace your thermostat with an 80 degree item (BMW p/n 11 53 1 466 174). Then replace your radiator fan swith with the 80/88 degree on (BMW p/n 61 31 8 376 440). It is also advisable to change your thermostat housing with the aluminium one you can buy from Goldwagen.
Lastly, you need to add 2 bottles of Redline Water Wetter to your normal antifreeze mix. This greatly enhances the ability of your coolant to absorb heat out of your engine castings.
Then make very sure your electric aircon fan, wiring and fuse is in 100% condition. You will have no backup if it fails.
I plan on doing this to my car soon. Worth a few BHP on a hot day.