It's amazing when I manufacture a kydex holster how some people will scoff at spending $50 on it when it has qualities you mention in your post. Yet, they'll spend $100 on a POS hybrid holster that is complete shit because some tacti-cool guy on YouTube uses it.
That being said, this is a great post and some great points being mentioned. As far a lumens on a light are concerned, use what you are comfortable with. I don't think 500 lumens is a bad choice. I run a TLR-1 HL with 800 lumen output. It's bright as all get out and probably a bit much for a handgun, but it works when I need it to. There are pro's and con's to leather and kydex, I just don't think they belong together. A lot of my customer base is from people wanting custom kydex holsters. If they request something I don't feel is "safe" or so outlandish it makes the holster impractical, I politely let them know.