The galvanic corrosion between the aluminum skin and the steel frame will accelerate with the addition of road salts. It will get in there and will be next to impossible to remove. Also be aware that many of the rivets and bolts are regular steel instead of stainless which would have been a much better way to do it but due to expense...
I drove the M3W twice in December the year I bought it. It hadn't snowed in weeks but the fine talc like salts were on the road and hadn't been washed off due to rain. Every time a car drives on the road the wind it creates kicks up a cloud of this crap. Your head is barely a meter off the road and you'll breathe it in. I was coughing for days clearing that crud out!
What's your mileage? Who cares. Is it practical? See #1. What happens when it rains? You get wet.
