So I been jabbering about this issue for a minute here. I finally got round to making a prototype. In no engineer, or electronics wiz... I'm a backwoods country goofball doofus... So it's ugly but you get the idea.
Mate, great work!! I'm really interested in your feedback regarding the tello's flight control during the low/zero light. In the video I noticed that you seem to have full control and the hover function is working well. Clearly the leds are improving the tello's ability to see the ground and manage a hover. I've got a similar project in the works like this, just waiting on the small lipos to arrive.
During modding I've found you can get approx. 3.2v off the USB port if you hack a micro usb connector and measure the voltage. I was looking at a way for the tello to power the leds itself. Obviously it would affect flight time but it would be neater and lighter. The issue is the driving voltage is a bit low for white leds.