Convert to new thread if you like...
I guess it would be easier to twist to constant-on if, say, the body of the light were clipped securely to your gun or something. To be honest, a switch like the Arc-White would suit me better, though I am kinda liking using it for short bursts of damn-bright-light. I wonder how long the bulb with last being turned on and off like that, though. Well, should do better in the A2 than anything else, as it has the soft-start feature.
Gads, that switch you describe would be a bear mechanically, but it sounds wonderful. I forget how the Arc LS4 is going to work, but I know it manages at least two brightnesses with one momentary switch.
I did some testing and it seems the A2 uses a 4.5V lamp, dunno what current, though it pulls 1.5A from the batteries. It also falls out of regulation about at 4.5V. Only problem with that is that CR123s seem to have a lot of life left at that point, they just can't hold their voltage at higher loads. 150-250mA driving a X5 head they handle OK, but stick a 800mA maglite bulb on a pair and their voltage sinks to 4.4 or so pretty fast. Some really dead 123s supply 4.5V to the X5 just fine, and drop to 1.5V under that load. Some sort of odd passivation effect in the batteries it seems. Something beyond just higher internal impedance.