CR123/16340 is almost a must for a pistol light. CR123’s will play at any temp, LiIon’s, not so much. Mechanical switch, paddle switch, button, whatever. Mechanical, no parasitic drain. This isn’t a lets go play outside type of light. One mode, ON. 200 to 500 lumens maybe. No blinkys, ridiculous and not necessary. As long as the emitter is white and not angry blue, it will work fine. If you need color rendition that is only rival’d by the sun itself, then you are using it all wrong. Pot it, pot it, pot it. After it’s potted, make sure the attachment hardware is bullet proof. If you fire your weapon and it goes flying off into the grass, then it’s only useful once.
Test it, test the hell out of it. Beat it to the brink of death. I don’t know gun laws in China, I won’t even try and guess. If it’s feasible to test random samples with a few thousand rounds, do it. Make it 5000 rounds if it still works after that.
Too many types of pistols to start making ones custom fitted for each weapon. Not to mention there are already a few companies doing that, expensively but, it’s being done. Something to use on full framed pistols with rails would fit many many many different side arms.
Finally, make it easy for customers to get quality customer service. Something lacking in a lot of companies now days. If I have to pay $35 USD to ship it back for repair or for a new one to be sent, I won’t waste my time and just buy elsewhere.