Im also looking for a way to make headlight more bright.
Gun flashlight and vehicle light is much stronger and I see no reason why headlight could not be as strong.
I have been playing around with settings for modArmorHelmetLight mod, I tried to use settings from vehicle mod, I even tried to use vehicle light mod and gun flashlight in helmet with no luck.
Adjusting LightValue have no effect, same on gun flashlight, vehicle light is possible to increase.
I have been looking to a way to make them less bright, so you can find dim ones early game and find/craft stronger ones later game. If anyone finds a way to alter the brightness, I'm all ears! I believe the only way is to extract and rebuild the light asset in Unity, but I have had issues doing that. Its still a side project for me, and failing all around still.