Layers are the key for this. Im domestic LE, I'm my area of work I can be woking at high-alpine 11,00ish, high desert, slot canyons, swamps and water ways and red rock desert. I base my selection process off of multiple factors. It could be lightweight/packability, breathability, warmth/weight ratio, etc. Most of the fabrics that work great for getting soaked and then quickly drying won't have FR capabilities based on the type of work you are doing.
For DA work I prefer cotton or wool base layers and utilities. But those are normally mobile approach short term operations so clothing selection for cold temperates will be more high-performance synthetics.
Sounds like the posting is leaning towards guys stepping off tarmac and entering the wild. I use the Med 3's rule for thinking about priorities. A medical emergency for peeps is normally 3 mins w/o air, 3 hours of exposure, 3 days w/o hydration and 3 weeks w/o nutrition.
Base layers - I prefer year round wool base layers. They have minimal stink, dry fast, insulate while wet and have FR properties. Injinji toe sock for me to prevent blisters and wick moisture from between toes. REI thin wool liner socks over the toe sock to add insulation or padding. Icebreaker, Patagonia or Helly Hansen are more preferred base layers, they are thin, durable, good price point, etc. I had some RHO layers that were actually to thick for my preference. But they were damn tough.
Insulating layers - Thin softshell layers are nice for a vary level of temperatures. I have been happy with the Patagonia MARS line of SS also ArcTeryx and Wild Things. Lately I have started using and liking some of the hunting brand manufactured clothing. Sitka makes some awesome pants that have knee pads built in. I love built in knee pads. They are always were you need them and not restrictive. First Lite makes some awesome pants and tops in merino wool. Nice and thin and they have taken a beating.
Wind/Water layers - I rarely wear full gore WPB materials when moving. Cause they really aren't that breathable. But wind and water can be major factors in hypothermia injuries. My favorite LW gore set is the ArcTeryx set. i can't remember if it is the alpha or bravo, just the lightest set they have. for resistant layers (not proof) the Wraith line is fantastic. Beyond Tactical makes great layers and well as Patagonia for these. Again, they are light and simple. not big, bulky and clumsy.
Woobie Layer - The wobble layer is for stationary work. Nothing sucks worse than hoofing it all day, getting sweaty and really hot from movement, too loosing that generated heat without a good layer that traps and insulates that warm air. Down is the king for this in general, but if you are working in a soggy environment and get down wet it is useless. In the winter when it is Cold/Dry I have a nice Patagonia down jacket. In more Cold/Wet environments i use my poncho liner modded with a head hole. The poncho liner stays in my pack 24/7 along with a sip-nylon 10x12 tarp. I have used them for casualties, shelters, bivy's and observation post. I also keep a small piece of ensolite the length of my hips to head to insulate from the ground and also work as improved splints.
Bottom Line - I don't care about the name brands or if it is what the latest tacticool guys is wearing. It needs to be durable, lightweight and work for the environment that I am in. We have a "loose" standard as far as the utility uniform goes. what I mean by that is we don't buy a bulk purchase of one set fits all clothing. It needs to fall within a prescribed earth tone standard color and then we received funds every six months to make individual purchases.
Any of these brands you will be happy with. either in a work utility or if you are a recreational outdoor junkie. Patagonia, TNF, Beyond, Wild Things, First Lite, Sitka, Marmot, ArcTeryx, Injinji, Helly Hansen, Smartwool, I/O Wool, Icebreaker, Jacks-R-Better and HPG. I am sure there are more, but that is what i see in a loaded duffel as we speak that sits in the g-ride for deployments.
Cheers
