I have used neoprene overshoes for years. These feature a zipper in the back and can be cut out for SPD shoes. Obviously they do nothing for the wet stripe up the back although a large seat bag like the minnehaha medium will help with that. I pretty much use them all winter long, with oversized shoes and 2 pair of wool socks when it is cold. As the temps approach zero I wear waterproof hiking boots. However, the fenders on my Brompton ( my only fendered bike) not only prevent road filth from getting on me but they keep the bike and chain a lot cleaner as wełl.