Put a screw down cap on the rear of the light, connected to the negative contact with the QTC in between, so that you can adjust the brightness without crushing the battery. Basically, put the qtc pill in the rear of the light, behind the negative contact instead of in front of it. This would also allow the light output to be adjusted before the head is engaged. If that makes sense.
Only issue would be isolating the negative terminal. Just make it out of plastic with an aluminum/copper insert.
Hmm...if the movable portion were designed to wrap around the rest of the tailcap to provide extra gripping surface, and if the center of the movable portion accepted a normal momentary switch, that would give a great range of functionality -- twist the tailcap to turn the light on at a certain brightness, and push on the momentary switch to get more brightness for for a few seconds at a time.