I have heard that if i load my trunk with over 100+ lbs of junk, it would increase traction.
The 3 series AH3 has around 200 lbs of LION batteries between the rear axles and during the winter storms I went to parking lots to see under what conditions I would begin to lose traction/forward movement. I never felt unstable or encountered moments of prolonged traction control warning lights. I think the extra weight does help for starts and maintaining traction.
Suggestion: take some time and get familiar with your tires and handling limits in a more relaxed setting (i.e.: parking lot). The more experience you have with the car, you will become better at anticipating the necessary action to take under snowy conditions.