Hiya,
I considered fitted the 4 BMW spots ages ago but it was going to cost some £500 from my dealer
so just went for the two. I was always a little non the wiser regarding the overheating issue, I think BMW were saying the extra light could interfere with the airflow. I'am sure also orginally you were suposed to have uprated gas struts due to the extra weight on the bonnet. Would definitely check regarding overloading the wiring and I reckon it would be better to fit the four onto a light bar than having individual brackets. I saw an S the other day and the lights were dancing around like flower pot men, just the 2 on my S vibrate a fair bit
Cheers