It looks like a great light that gets a lot out of a MT-G2 . Love to see beamshots, 70klux throw with a huge hotspot must be impressive. It looks good too!
I have been on the fence on what MT-G2 light to choose (7G10, S2200 and then this) IMO, the Niwalker brand is the most well-made among the 3, it has a magnetic rotary switch like the TN31, and a 2420 lumen output in a single led light. Huge hotspot as you said, very nice combination of throw and brightness.
I think Selfbuilt’s video review is the pre-production version. The production version is a revised 02 and has a constant-current circuit design for constant output, among others.
Some quick and dirty calculations, please correct me on mistakes: The MT-G2 has a Vf that is about 6.5 V at 4A current (this is my led-current guess in this flashlight), various resistances in the flaslight eat say 0.3V, the driver may eat another 0.1V so two batteries in series must deliver 6.9V under load. A popular Li-ion (Panasonic NCR18650B Protected 3400mAh) under 0.5x4=2A (there are two series, so 2A per serie) load stays over 6.9:2=3.45V for over 50 minutes.
So I'd say yes, a driver can be be had that keeps the light in regulation for quite some time.