Re: Any interest in a AAA "flood" style light?
I probably won't be rushing in to buy one right away as I'm trying to hold back a bit at the moment, but I'd certainly consider myself interested, both in the light itself and the project. I'll be following this thread with interest and wish you luck with it.
I find some of the "I am very interested in your Thing although I would prefer a DifferentThing" comments somewhat amusing. Try not to get too sidetracked. Keep it simple. Keep in mind the goal and the use-cases you have in mind (close-up, indoor use, like in a tent). I think for those uses it sounds like the design as it stands is pretty much perfect if it all works as intended.
One thing to consider from a design perspective is how you would imagine people will carry this? Will it be in a pocket with other junk, or perhaps on a keyring? Or maybe clipped onto a shirt pocket? Would it be reasonable for people to hold it in their teeth for hands-free usage?
I don't mean that you should lock onto one at the expense of the others, but take one points that has been mentioned already for example: the diffuser will be prone to scratching. This is mainly a risk if it's kept in a pocket with a lot of other stuff, especially if it's on a keyring. One suggested solution was a cap which can go on the tail. Unfortunately, that design will not work if a keychain is attached, unless you find some way of working around it. So, if the intention is that it will be on a keyring, you need to think about how to stop the lens getting scratched and a cap is not a good solution because it doesn't fit the use-case. Don't adopt a solution without thinking through the root problem that it's intended to solve: in this case the root problem to be solved is not scratches, it is the use-case "I want to carry it in on a keyring" or "I want to carry it in a pocket with hard & scratchy metal objects like keys". A follow-up use-case might be "I want to quickly detach it from my keyring and hold it in my mouth so that I can use both hands without carrying extra equipment such as a headband", or else you might want to eliminate the possibility of keyring carrying altogether (which has some advantages, namely the cap solution isn't ruled out, it's easier to make it tail stand and it's easier to add a switch to a future version without changing the design or having a highly inaccessible recessed switch), but at a more obvious cost.
Sorry if the above seems obvious to you, but the poor standard of industrial design by mainstream light makers is one of my pet annoyances. Most of them are just a collection of features that serve little or no useful purpose at the expense of things that might actually be useful, including just "more simplicity", which tends to make things more intuitive to use and more reliable. The last thing you want to do is get sidetracked by trying to please everyone that posts a suggestion, because everyone wants something different and you can't accommodate everyone without making sacrifices (well sometimes you can, but it's rare). You're going to have to make some compromises, but the trick is to compromise on things that don't matter for your list of use-cases, while keeping that list simultaneously as broad and as cohesive as you can manage.