Another report of success.
I recently bought a '15 Leaf SV, which did not come with the auto-headlight option, which was a disappointment. However, after reading through this thread, I moved the combination switch and ambient light sensor from my '09 Cube (which had auto headlights and fog lamps), changed the appropriate settings in Leaf Spy, and the headlights now come on when the light dims. Very happy.
For those who come next... Having tried combination switches from 3 different vehicles, I'm fairly comfortable saying that if the style of stalk matches, the switch will fit and be recognized. I swapped the switches in both directions between the '09 Cube and the '15 Leaf. I also tried the switch from an older (07? 08?) Sentra or Altima that was at a local wrecker -- It fit and was recognized in the Leaf as well.
Which brings up my other discovery to report. While the fit of the switch, and it's pinout appear to be standard, the internals are not. The junkyard switch does function, but the vehicle it came off does not have a rear window wiper, so that function is of course missing on the stalk. When I disassembled the original Leaf switch and the junked switched, with hopes of swapping the wiper stalk, I found less standardization than I hoped for. The circuit boards were different, and the junk switch (which supported auto headlights) did not have unused contacts for the rear wiper. Disassembly and reassembly were straightforward, though.
The final word being that if you're looking for the right switch, don't worry too much about the specific part number. Just make sure it has the functions needed. From what I can tell, it will work. Extra functions that don't exist on the target Leaf will be ignored. Functions on the target Leaf that are unsupported by the combo switch will be unavailable. And building a frankenswitch won't work.
So for now I'm living without the rear wiper function, and will troll the local junkyards for the unicorn switch with auto lights, no fog lamps and a rear wiper.