I've been hunting and fishing in Maine, NH, and VT since childhood. Not exactly the rocky mountains, but plenty cold and wet enough. I'm also a homeless person and live the way people camp full-time and have for years. Here are my thoughts.
- Thermal underwear is unnecessary. Underwear is the thinnest layer of clothing you wear, and the closest to your body. It is the least likely to get wet and the fastest to dry if it does (such as if you layer improperly and get a little sweaty while chopping wood.) I wear the same Hanes polycotton underwear and tshirts from Walmart year round no matter what I'm doing and have never had any issues even when miles from civilization in a noreaster. I do wear wool socks, but only as a boot liner over normal polycotton socks. The job of underwear is scent control, you change it every day so that you don't stink up your heavy, expensive clothing. If the underwear itself is heavy and expensive it defeats the purpose.
- The only shell I need is a raincoat. The job of a shell is to repel moisture and wind, a raincoat does both exceptionally. My favorite raincoat is a buckskin colored Helly Hansen raincoat that is knee-length and hooded and cost me $79 at Sam's in Brattleboro and, in conjunction with as many cheap polyester and wool surplus insulation layers as I feel necessary underneath, is all I need to brave the elements whether a freezing November rain or a howling -5F January night. I only use it in the cold months, from April-October I just use the rain poncho I keep in my pack. I threw all my expensive winter parkas in the donation bin.
- A baseball cap is a must because it keeps rain off my glasses, fits under a hood, and I keep a flashlight permanently affixed to it. It should be polyester so it dries quickly. I can wear a beanie over it for extra warmth but with my hair it's rarely necessary.
- Boots, there is absolutely nothing I cannot do in uninsulated Bean boots. I wear the same pair year round. They're the perfect size to fit acceptably over ordinary socks, but large enough to permit an additional wool layer in winter. My feet are never cold when I'm using them no matter the weather. When I'm stationary, such as ambush hunting, I just wrap my feet in a section of blanket. I do not see any need for specialized winter boots, and I don't see how you can keep the insulation clean unless the liner is removable, which it often isn't. Winter boots also frequently fail to function well with snow shoes. Snow shoes are indispensable up here. I also often wear "water socks" if it's above 30 degrees. These are very comfortable, inexpensive, moccasin-like footwear that allow me to move silently and increase the rate of run-ins I have with animals while moving. They weigh nothing and I keep a pair in my pack at all times. Combined with a walking stick to serve as a third leg to distribute weight to, I can get within Glock distance of deer and black bear very easily.
- I EDC a large survival fixed blade every day. My current favorite is the "Drop Forged Survivalist" from Cold Steel. It's a homegenous chunk of 52100 steel with no structural weak spots, and I can baton it through anything and fell trees 8" in diameter with it if I have to. That combined with a small folding knife for whittling and dressing game are the only blades I carry. I don't bring a tomahawk or an axe unless I'm really going to need it.
- My sharpening device is my own invention. It's a 4"X1" soft Arkansas stone affixed to a 1"X1" aluminum rectangular tube, with a leather chromium oxide loaded strop affixed to the other side. The tube is just long enough to allow for the use of plastic angle guides. The tube provides clearance for your fingers so that you can use the entire length of the stone, unlike if you were just holding the stone directly. This also promotes even wear on the stone so it won't take on dished character. Additional angle guides can be stored inside the tube. Beyond this I also carry a 6" triangular file which only weighs 2.8 ounces IIRC for repairing serious damage, it's narrow enough to bite carbon and most tool steels using only one hand without having to clamp the blade to a bench. A chainsaw file works too but is too easy to screw up with and doesn't do points well. The progression of file>soft Arkansas>Chromeox strop can produce edges that are about 90% as effective as anything I have ever achieved even with the finest Japanese water stones or SiC paper. Using only the file and my sharpening device I can take virtually any edged tool in any state of disrepair and bring it up to my standards in less than an hour.
- Fire starting is something I've never gotten fancy about. I practiced the bow drill method enough to satisfy myself that it is very easy. Beyond that I just carry bic lighters. They are extremely reliable, cheap, and lightweight, as countless smokers will attest. In wet conditions there is always birch bark around the corner and dry firewood inside a dead standing snag. I have never had any difficulty making a fire in my entire life even when deliberately doing so under the worst possible conditions.
- "Luxury item" is a good description of a camp stove. I use one every day, but only at my truck. I've never brought one camping. I just bring some jerky and trail mix and vitamins and find that sufficient. I use a very thin steel lightweight mug to melt snow in and boil water in. Sometimes I roast wild meat and fish over a fire in small pieces and just dip them in barbecue sauce packets.
- For water I only carry two 8 ounce Poland spring bottles from a gas station a year ago. There is water everywhere up here so there really isn't any need to pack alot of it. The two bottles allow me to distribute the weight better. I also carry a lifestraw, but rarely use it even when hiking all day.
- For taking a dump I put together Ziploc bags with 5 paper towels each soaked in the same baking soda solution that I bathe with daily.
- Everything else in OPs post I agree with. He clearly knows what he's doing.