I personally do not think that the oddities automatically rule out the kit for a tactical/self-defense type light.
With a spacer or washer, the tailcap works fine in my old SF 6P. The switching off thing when fast pressing occurs only when using the side button. And you use that button to access low mode, which IMO is a secondary option. The primary functions, max brightness and strobe, both have worked every time with no glitches. Even with the side button glitch, it takes only a little training to press the button just a little slower. Then the light has always stayed on, just at a step or two higher intensity than the lowest setting. If that is too bright, you just hold down the side button to ramp down the intensity.
The power draw from the tailcap even when the light is off is my main concern. So far, it looks like the light will last at least 2 weeks between charges. But I would recommend 1) using rechargeables instead of primary Li cells for cost savings and 2) regularly checking the light for function and the cells for suffiicient charge.
In my review, I added the following tidbit:
OpticsHQ informed me that the tailcap power draw is 0.5mA to 1 mA. That translates to 12-24 mAh per day. 16340-sized Li-ions seem to have a typical capacity of about 550 mAh. If we operate the cells to maximize cycle life, then we might charge them to 90% capacity and discharge them down to 20% remaining capacity before recharging them again. That gives 550 * 0.9 * 0.8 ~ 400 mAh effective capacity. And that gives an operating life of a TLS-equipped flashlight of about 15-30 days.