Well, I'd agree with all of that in general (bentirran). But I've been carrying the round flashlight MAG Solitaire at work, with the original bulb upgraded to Tektite LT-3 UB LED thing. The exact purpose of the upgrade was the possibility of complete consumption of the partially discharged AAA batteries, left from the other toys. It works nice, but I don't like its size for EDC. I saw Fenix LOD CE, and yes, it's a bit shorter, but noticeable bigger in diameter than MAG. I needed something to keep it comfortable on a key ring in my pants pocket. So, a flat flashlight with shielded bulb had the best fit.

Another thing I like in the 2016 based flashlights is the simplicity of the battery holder. It's easy to attach a couple of wires from an external power source to power the LED circuit. 5-6 Volt is very common in modern electronics. So I'm trying to have all of my gadgets powered in this range. Try that with any AAA flashlight.

Regarding the batteries. My job is IT guru. All of the dead PC's ends their path in my office. They use 2016 batteries for the BIOS power, so I have an unlimited supply for now

By the way, the rechargeable coin cell batteries do exists in the nature: http://www.saveateagle.com/b-332.html?ovchn=OTHER&ovcpn=Froogle&ovcrn=B-332&ovtac=CMP