I also think, that ‘hotrod’ (which is the most trending kind of lights here on BLF) is impractical for headlamp use. I think BLF should not specialize only in that kind of lights, any new designs (with its own application goals) could be highly welcome addition (e.g. DBSAR’s lantern). They don’t need to be maxed out regarding raw output and/or throw numbers. (Also, I would even happy to see some custom stuff, which would go to E27 lamp sockets, because in middle Europe, E27 light sources tops around 80 CRI - but that is a bit different story.)
For me, a multi-emitter headlamp could be one, which I would welcome, if I’d see that as a BLF project.
I think, some of us can agree, that a Nitecore HC65 headlamp could have been a very good one (some of us thinks it even IS), because it has multi emitters, thus, it can serve us good in a bigger variety of situations. I like good output levels, but I am mostly a tint/beam snob. So in this regard, unfortunately, the main light source of the HC65 falls under greatly. Also, as I remember, beams are a bit misaligned for the auxiliary light sources.
Since a bit more than 2 months, i started to fiddle with some Yajiamei PMMA TIR optics in Convoy S2+ lights, and I think, there is a great opportunity there to deal with. For most people, a very creamy flood is the best option in a headlamp. In most cases, I also highly prefer this kind of flashlight beam. However, most of the headlamps are still with SMO reflector, which are suboptimal in this regard.
While I fiddled with those Yajiamei optics (the ones for XP-L and XM-L, with the physical size of d=20mm and h=12.8mm, no stents), I recognized, that the greatest addition to headlamps could be these optics, as if the headlamp is designed to make optics swapping easy, we could have our headlamps just fine-tuned to the way we would exactly like it, regarding the beam.
And if there could be e.g. 3 emitters in the headlamp with this exact kind of optics with a d=16mm MCPCB base, the possibilities of customizations could not end easily.
For example, a specific combination (this could be one which would be on my head near all the time):
1. slot (emitter + optics combination): clear optics, 5 degree beam width: would be suitable for Nichia 319A R8000 5000K, which are rather R8320 in practice, and would give a decent output. 5 degree clear optics make a very dim spill (much dimmer, than with a same size of SMO reflector), so it would be a very efficient thrower, when it is needed to make out some reference objects far away.
Alternatively, 10 degree beaded optics would also suffice.
2. slot: beaded or frosted optics, 30, 38 or 45 degrees beam width: would be suitable for quad Nichia E21A R9080, 4000K or 4500K. Would be the ultimate reading/assembling/studying light, when accurate color rendition is very nice to have or even ‘critical’. Frosted optics provide the most creamiest flood, but they put considerable amount of light into the spill. If we would like to keep most of the light in that medium sized hotspot, beaded optics are better for this.
3. slot: beaded optics, 60 or 85 degree beam width: Cree XP-E HE Photo red (~650-660 nm), as this deep red could preserve one’s dark light sight pretty well.
Alternatively, a quad Nichia E21A of 2000K CCT could make a great service here (a big gain for detail recognising, but some sacrifice of the dark adapted sight).
Another one could be (this one could be good for CJW):
1. slot: beaded optics, 25 degree beam width: same Nichia 319A, as mentioned above, but now a wider, more generally usable beam with moderate throw.
Alternatively, if someone prefers to have a relatively strong, but wide spill, while still having a good throw, I could recommend 15 degree frosted optics.
2. slot: beaded optics, 38 degree beam width: XP-E2 green emitter.
3. slot: beaded optics, 38 degree beam width: XP-E or XP-E2 red emitter.
Again, I think, it is not needed to produce these exact variations, but the most important could be to make these possible, just the way I described them (top priority on modularity). I believe, many of us could make one or two distinctive set of requirements for their exact liking.
Regarding batteries, having 3 of these slots, I think, the best option could be single 21700. A sophisticated driver PCB design could even let chose max. current per each selected emitter to e.g. 0.3A, 0.8A, 1.5A or 3A depending on the power class of the emitter, which would be intended to be used. UI could be dual switch: one for the output levels/modes, one for the emitter selections (e.g. 1. first, 2. second, 3. both first and second, 4. third).