All-season tires don't make a lot of sense for your situation. Why not have the very best (dedicated snows and summer performance tires) if you are going to have two sets of tires? Two sets of wheels is also a no-brainer IMO. Buy a used set off of this forum to save a little. As Ben said, it's way easier to swap wheels vs. mounting and dismounting tires on one wheel set. You can then sell the second set of wheels when you get rid of the car. I hope this helps.
'13 M3 - Silverstone II - Sold
'04 M3 - Jet Black - BBS E88, KW Clubsports