To clarify the N54 has an electric waterpump with 2 times the wattage of ours and twice the ability to flow but indeed are both electric.
In my opinion it is one part I will wait to fail as once you start letting a bmw mechanic mess around in taking a perfectly good part off that has been goin strong you add in the error of his mistakes and crappy work, defective part, loose connections etc that you otherwise wouldnt have had. You cannot beat a factory installed part in an engine and if you are running with no problems I would leave it. There is a way to check engine temp through computer by using the tachometer reset button---youll have to google as I only know it for the e60.
The only prevenative stuff I would change other than coolant flushes every 30k are hoses if something else goes. My radiator went out of warranty and they were nice enough to change the two big radiator hoses. If my pump goes I would change all the hoses in that area. I use gummiphledge on the hoses but those tend to wear over time due to the extreme heat