I asked about a separate battery box headlamp in an earlier discussion because they were available from surplus dealers for ~$10. They are the very lights that we used fighting wildfires when I was a lot younger. They take 4 D cells and run all night long on a single set of alkaline batteries. They used incandescent bulbs with an E10 screw thread socket. I used an LED bulb in mine when they first came out; although I have no memory of what year that was nor whether I was still fighting wildfires. I'm so used to using one of my annual issue head lamps, that I bought from the US Forest Service out of the last check of that season, that I have trouble seeing the modern ones as more than a locator light like you might wear on a Personal Flotation Device (PFD). That in spite of the modern headlight giving off a lot more light for less than a quarter of the weight of the 4 D cells. I replaced the incandescent bulb with the best LED emitter assembly that fits the headlights E10 screw threads I could find and it really gives enough light to work safely with hand tools in a dark night. I've done repairs on fences, helped set up camp for 120 high school aged kids, and worked a radio all night with no other light. I can't explain it but I still use it and still enjoy the way it performs. When I turn the bezel to adjust it from wide to narrow beam the transition is even with no dark rings in the pattern. USFuS (us fuss) set out to make a head light for firefighting and even with all the advancements in batteries and light technologies just changing it to the LED emitter has kept it up with the need for a long duration, hands free, night work light. Working a radio all night in the cold gives you a new appreciation for the saying often uttered by the old timers. "Real radios glow in the dark, keep you warm, and you can read the manual just by the light from the tube/valve filaments.First, just as an 'aside': When I was young, I did once get a nice stock replacement dash toggle switch (for another lighting function) for my car, mounted it along side the existing switch, and controlled my back-up / reverse lights with it - not so much to disable them (although certainly that as well), but rather to turn them on at will to provide rear lighting. This also allowed me to switch them on when driving to enable me to send "get off my 'a'' in Morse code. Just kidding about the code, but I didn't need to send a coded message. Merely switching them on and off, perhaps multiple times, would usually produce the desired result. Had I been as cool as Steve Mc, I would have had another to kill my rear running / brake lights. I'm pretty sure that was an ol' moonshiners' trick. Not that I would know, but I did grow up in the deep South.
Having lived in your area (a bit North - Owings Mills area), and often regularly worked many points well North of there (up to and including N. Eng and MN in Winter, and even bloody Alaska in Jan. several times!), it is a sincere personal objective of mine to never deal with such snow (or temps) again. That photo alone gives me nightmares.
That said, regarding your question about flashlight batts and cold temps, only 2 things occur to me. One is to optimize the power source for the conditions by using only lithium primary cells (CR123A, etc) which are optimal for cold environments. The other is, rather than trying to optimize heat dissipation as we normally do, to do the opposite: reduce heat dissipation by covering the light housing with something with thermal insulating properties - not unlike those things people place on their aluminum cold beverage cans. This would help retain / conserve the available heat generated instead of it's going to waste, and the combination would have to help some (relative to a naked Al, alkaline-powered light) in such conditions. Barring use of active heat sources, that's all I can think of, aside from use of lights with a remote batt pack, which would open up other possibilities, but would likely be inconvenient.