All Great ideas. Layering I have found works best in brutal weather. Bibs and layered coats work great but a full suit is one of my favorite options when it gets brutally cold. Big downside to this is going to the bathroom! I have a insulated gore tech suit (Over 20 years old!) that comes out in the most brutal of weather days with attached hood and full face mask does the trick for me. A good parker with hood keeps my neck and head heat in.
Polypropylene base layer, t-shirt and a fleece sweatshirt, pants and or parker and full suit with hood. Balaclava, neck warmer, glove liners and waterproof gloves.
Some clothes can get bulky but if your gun hunting it is not that big of an issue.