However, the flashlight will have lots more power if used with a Lithium battery instead of an alkaline / NiMH battery (5A @ 3.6 V) vs. (0.5 A @ 1.5/1.2 V).

Good to know! I already have the NiMH batteries + charger on hand though used in other bits and bobs, so it will be more cost effective for me to use those over buying new 14500 Li-ion batteries. Will try 14500s if I have any troubles with the power!