I’m against onboard charging for weapon lights, especially pistol lights. Size matters more, and any additional complexity is another thing that could fail. I also don’t want to leave my pistol connected to a charger and possibly unattended. Swapping the battery and putting the used one on a slot charger is almost always going to be a better solution.
I’ve seen a number of people claim rechargeable batteries are less reliable than primaries, but other than shelf life, I have not seen any basis for believing that. Furthermore, it’s not meaningful to compare capacity in mAh at different voltages. A comparison of mWh is a more meaningful representation of their capacity, and 2665 mWh isn’t that much less than 3239 (1A load used, which again is more power from the higher voltage Li-ion).
I’m going to reiterate my suggestion for 18350 support here. It trounces the other small cells with 4158 mWh - that doesn’t mean it shouldn’t support CR123A. Ideally, the light would support CR123A, 16340, and 18350. The light should be regulated such that they all produce the same power and heat.