Ok well here's the quick rundown.
You can't use more CR123 cells. You can use 18650, 17670s if you can find HDS 18650 tubes or buy the HDS 2x123 tube from lighthound.
It's about 2 hours runtime on level 1 on 17670.
You can get Ti or SS rings for the bezel. There's nothing like the Ra Twisty for it.
You can get a UCL from flashlightlens to replace the plastic one. Or go Sapphire.
You can upgrade the LED to the latest U2 bin for about a 10-20% increase which is not visually noticeable.
You can send it to milky to change the reflector to an optic that throws better.
Again like the replies in the other thread said there's no real way to increase brightness or runtime. If you want to change the beam it's gonna be tough. The last reply in the other thread sums it up about the beam pretty much.
Also there's a bunch of threads on Novatac lights, a quick search pulled it up. I just did it now. This light doesn't lend much to extreme modding. But putting in Glow rings and new bezels and lens are well documented and (relatively) easy to do.
If you really want to change it up you can put a P7 in it.