This is an area that I have been struggling with and refining over a period of many years.
The majority of my hunting is mountain hunting and I am always going up fairly steep stuff to arrive at stands that I will be spending a number of hours at.So the heavy Wool or the heavy lined bibs and parka's don't work for me.If I wear them from the time I start out I will be drenched with perspiration in short order.Also I don't want to carry the weight of those type of garments.
So the solution for me has been pretty much to always have a pack on my back and to have layers of light but more clothing that I can make adjustments with.I have 200 weight Ulfrotte/wool power bottoms and tops that I will wear with a thin unlined wolf skin pants or supplex nylon pants,same for my upper body with the ulfrotte,I will have wolfskin jacket or thin windproof fleece.Once I get to where I will be on stand when it is really cold I will put on one or two more layers of wool long under shirts,ulfrotte,smartwool,minus 33,possibly a patagonia micro puff vest or micro puff pullover,or in the really cold an integral designs dolimitti jacket or patagonia Das jacket.The final layer will always be unlined wolfskin or thin wind proof fleece.I will put a second pair of long under wear on and patagonia micro puff pants with wolfskin unlined pants or windproof fleece as the final layer.
I will have an extra pair of dry socks to put on ands I will have handwarmers and feet warmers to use as well,if it is brutally cold I will have Ice Breaker boot blankets with me.I also have multiple wool hats,Baclava,neck gator etc.
This may sound like a lot but it really is not from a carrying weight perspective.No more weight than heavy weight wool bibs and parka,I believe considerably less and a lot more flexibility in various temperature ranges.
Things that are on my short list of possible future purchases are a Helly Hansen Fibre Pile Union suit.Those things look seriously warm!I may also purchase a light weight synthetic 0 degree sleeping bag to crawl in to versus a much heavier and one dimensional Heater Body Suit.
I don't have it licked yet but I believe I am getting close.