The switch doesn't necessarily have to be at the same place as the electronics. Just add two more threads in the cable.
It seems the electronics are in the battery box, and there are connections to the headset for
Main LED power
Battery indicator LED
Thermal sensor.
As someone suggested here:
http://ukcaving.com/board/index.php/topic,8806.0.html
80lm for an 'extra low' power setting seems pretty excessive.
Maybe OK for a MTB light (which I understand the manufacturers also make), but for a
caving light?
Personally, inspired by discussion on one of the Zebralight threads, I spent a few hours last week adding an ultralow setting to the driver firmware for my caving light, and that was because I thought that with LEDs having advanced from the early 20lm/W luxeons I started with, having had my low power setting creep up from 2-3lm to 10-12lm over the years, it was time I stuck a proper moon mode back in.
But then I guess that not running at 800lm at full power, I do have some dark adaptation, so I can still see adequately with a handful of lumens.