I went to Tire Rack and ordered winter tires, wheels and TPMS Mounted and balanced. I have the 18” staggered wheel/tires on my 135i for summer but I got 17” wheels and 225/45/17 tires all around for winter. The winter tires ware really quickly on dry pavement so you can rotate them. It sounds like I am a little more aggressive driver than you and I think the winter setup is fine. I have a couple floor jacks and air compressor and change back to summer if no snow is forecast for a week. I can change all four wheels in 20 minutes.
135i – SGM/Black Boston Leather/Aluminum Trim - 6SP MT - Sports Package - Premium Package - Cold Weather Package - Premium Hi-fi System - ipod/USB adaptor - Comfort Access System