To the original poster, I have the P7 set up and we had a decent storm hit last week. The car performed just fine where the roads had been somewhat treated with sand even though not fully plowed. However, I could tell and I was not surprised by the fact that it did not give me the confidence it would perform in deep snow.
While two 45 lb free wieght plates (availsble here in the states for instance at any large spporting goods store will help (old mustang drivers trick and you do not need to "load the trunk with junk", they will lie flat and you will only lose 2" of clearance), I think you need to rethink the all seasons and get dedicated snow tires. When things gt that bad, I have the option of using our X5. Without that, I would get snows too.
2013 F30 335i 6MT M-Sport - Blk Saph. / Beige Lthr / Wood Tr. - Tech Pk - VSS M-Adp. Susp. M-Perf Stainless Exhaust M-Perf. brakes