I have an update on how to modify the Maglite 2AA w/NexStar bulb to get an immediate spotlight when you turn on the head.
A plumbing faucet washer known as the "3/8M Flat Washer" will spacer out the reflector just right so that as soon as you turn on the head you get a cat-eye shaped spotlight. When you turn the head a little more, you'll have an even more intense spotlight with a symetrical, nebulous corona. I found two different brands of the washer, which vary slightly in thickness.
The washer hole gives the bulb plenty of clearance and the outside diameter of the washer is such that it requires minimal force to install.
To install, you either 1) remove the head and tap the washer down inside the head, past the threads, until it sits flat against the back of the reflector, or 2) take off the bezel, reflector, and lens, place the washer against the recess in the head, and screw everything back on.
There is a slightly larger washer known as the "3/8L Flat Washer" (by Danco, UPC#0 3715535068 1), which also works but it must be forced down the threads. The resulting beam bypasses the cat-eye and immediately goes to the intense-spotlight + symetrical-nebulous-corona type beam.
Sorry, I was unable to obtain the UPC# for the "3/8M Flat Washer" from my local plumber, but I get the impression they are common.