Install a snow plow and you will be good.
Seriously though, i will probably continue using the summer tires (PS4S) as long as i can because it does much better job at evacuating water than all season/winter tires; have a set of those too. I have learned to accept that the m3 is not going to have much grip during winter season, but it is no worse than 80% of the other cars on the road. Just be easy on the throttle, brakes, and be alert of other drivers.