Interesting project. Are the flashlights aligned to overlap their hot spots on the ground, or could they be set to spread out a little so as to use more of the camera's field of view? It would be interesting to see what a headlamp-style optic would do, though it might be too floody at higher altitudes. Right-angle headlamps wouldn't fit the present brackets. The advantage with using flashlights is that they are pretty simple when they fail or need recharging, and can be rugged. But I think the ultimate solution here will be a customized lighting pod, trading all that extra aluminum for more battery power to better match the drone's endurance. It occurs to me that PWM here would be very undesirable, as you wouldn't want motion on the ground to be confused with flickering light source.
Bill