The Arc LS, rev1 (LS1), on a single AA is by far the brightest single AA LED light so far. The Arc LSes get the best runtime performance from Lithium AA, to about 6.x hours bright, then nosedives to moonmode. The pics on the web no not do it justice. My newly arrived LS second, has replaced my infinity. I will get the ultra for it double brightness and 20 hours runtime, for a backup light.
The single AA packs have been discontinued, as the rev2 (LS2) doesn't work well that way.
I would say it is more than possible to make a single AA light with an LS1 module, using NX05 optics. Best runtime is Lithium AA. If it could be regulated, then that should increase usefulness somewhat.
Don't even think about using a 5 watt LS for this.