Thanks for the feedback so far… To answer a couple of questions…
100m wide throw would be ideal, but certainly not essential.
I will be holding the flashlight in my hand while riding, because you move your body around quite a bit when riding a Onewheel, so head mounting isn’t ideal. Mounting on the Onewheel also isn’t great because a) the angle is too close to the ground, and b) if you fall off, it’s going to inevitably get ripped off.
@sp5it suggested a bike light because the run time is longer. The Nightfighter BT40S looks like it’s no longer available, but was powered by a 2S2P 18650 pack, with a 5,200 mAh total capacity. Each pack would therefore have ~2x the capacity of a single 5,000 mAh 21700 cell. When riding a Onewheel you stop fairly often to take a short rest, so changing out the battery wouldn’t be a problem at all. The form factor of a bike light isn’t great because it would be difficult to hand hold.
It sounds like a multi emitter design might be best if they’re more efficient, and these seem to usually be TIR based. The BT40S is a good example of that as well. I do like that the BT40S was supplied with two TIR optics because I’m not yet sure what angle would be best to ride with. If I’m hand holding, I can freely move the light around to scan the upcoming path, which might allow for a tighter beam.
I think I’d favour something that is customizable so that I could try different beam shapes by changing out optics / reflectors and maybe even between single and multi emitters.
Thanks again for the feedback so far.