This thread is getting long, but:

1. Only the FET+1 version of the D4v2 drew 18A and from what I can tell, Hank gave up on that some time ago. The present CC drivers take 5A, 7.5A, or 9A depending. I think mine is 7.5A. No idea about the boost driver.

2. The highest discharge 18350 that I could find with a quick search was 10A (Hank offers an 18350 tube for the D4v2), same as I see for USB charging 18650 (Vapcell P1835A). I also see a 30 amp USB-C 21700 (Acebeam IMR21700H-400A) so for the D4K, that concern simply goes away. Anyway, if the user wants to give up the “hand warmer” mode of a light to have some more flexibility in battery choices, that should be up to the user. So I think you are simply trying to rationalize a shortcoming of this light. My other 18650 light (Fenix BC21R) works fine on both protected and unprotected cells. It came with a protected cell and it’s annoying to not be able to interchange that cell between the two lights. The BC21R’s brightest mode also heats up too fast to be usable, so the protected cell isn’t the limiting factor.

3. All versions of the D4v2 appear to dent up batteries. The boost version with its flat spring seems to have even worse problems, but I don’t have one so am not sure of specifics.

4. I’m not claiming that the D4v2 is too big or heavy. I find it just right, and I’d actually prefer it slightly bigger, to accomodate protected cells. All I’ve said is that whatever Hank is after, it doesn’t seem to be weight or size minimization. The D4v2 is slightly bigger than a 1xCR123A McLux Sundrop for what it’s worth, and weighs about the same because of the Sundrop’s heavier titanium construction. And I found the Sundrop to be just about perfect for its era.

5. I’d consider a mature light as one conceived holistically by the designer in the context of a deep understanding of its intended usage, not compromising its usability as a light source in favor of party tricks or heat gun functions. The Spy 005 was radical but at the same time mature as conceived, even though some bugs then had to be worked out of the implementation. I’d say all the later McLuxes have the same sense of maturity. McGizmo is a real Zen master of flashlights.

6. As for Hank offering lots of hardware options, that is somewhat true. There is a 35mm battery tube, and a 50mm, and a 65mm. So why is he (and apparently you) he so opposed to a 70mm? I’d buy one. I’d also probably buy a D4K, if it could hold the Vapcell P2150A which is a 76.6mm 21700 with a built in power bank function. (Hmm, maybe that can fit into the D4Sv2 with the 26800 tube and a spacer).