In fact, to keep things even lighter, I would consider something like a Zebralight H600w or Armytek Wizard Pro Nichia and use it with a cold weather 18650 battery such as this Fenix which is rated down to –40 C/F.
The weight savings would be significant, and it would be a significantly smaller, simpler light with less that can go wrong.
I would just avoid the cheap 18650 headlamps that aren’t regulated or temperature controlled.