Another thing I’d like to see would be a USB powerbank head for the S2+. Unscrew the LED head, screw on the powerbank head, and you can charge your flashlight cell back up or use it to charge your phone.
I’d plump for 1A input to charge an 18650, with 2.5A output for a USB device. That should work with any decent 18650 from the NCR18650B on up. Think of it as a Thrunite C2 done right.
Taking the reflector out of the S2+ head and replacing the lens with a flat cover plate should leave plenty of space. If I had the skills and resources to design and build a couple of boards in 16 or 17mm size, one for a TP4056 charger and one for a 3.7V to 5V USB booster circuit, I’d be doing it right now 