With todays improved technology 1D lights are not as needed.
Oh, I agree with all of that, but I think some of us are coming at it from the other direction.
It's not that we want a great light, and are thinking a 1D would be a good way to provide it.
It's that we have spare 1D cells lying around, and would like to use them up.
Ideally, in a low-intensity, vampire/cockroach unit. Something that would put out 0.5 lumens for months and months on end, for instance.
Or the "Fenix D01" idea--a tough, low output light in the 10 lumen range that would last for weeks.
I, too, wish there were a light in this niche.
Actually, I would be happy with a simple cylinder that let me drop in a 1D cell. Then it has a threaded cap on the top that is pre-tapped for a Fenix E01 head.
You thread your E01 head in there, and you have your D01 just like that. Lasts about 10 times as long, which is pretty long to begin with.
I would far rather have that than going for a stubbier Maglite--I don't want the high-output, or the reflector, or the variable focus. Just a simple, reliable cockroach that will run on my left-over D-cells.