<<The advantage of an electric fan is that you are no longer dependent on engine RPM, for example, stopped in traffic when you need the most air flow, >>
I have often toyed with the concept of modifying aux fan trip to the speed sensor circuits..
Say, at zero to 15 MPH specs...
Also have considered speed sensed high fan for a/c at stop/idle conditions ... this would be a simple speed sensed relay paralleling the dropping resistor [ low to high speed fan] when in traffic/stop lights, etc..
You will notice that Benz is now using electric fans [ puller] and also using a/c compressor synced activated aux fans....