It's definitely that time of year again...:-)
Upgraded bulbs are always a positive modification...Philips do a good range of enhanced lighting
Not sure if I'm understanding you correctly but if you press the DSC light it should invoke the 4 wheel drive to ensure stability is maintained but not taking full control of the vehicle...e.g if going off-road for example, where you wouldn't want the DSC taking over?
Good luck with the work on the X5 in this chilly weather