Y'all are working entirely too hard at this. Adobe created the CinemaDNG & the photography DNG specifications. Use their tools.
In Adobe After Effects, create a new composition.
Select the first .NEF file, Import As: Footage, check Camera Raw Sequence.
Very Important to bring the hotness. Use Camera RAW to initially grade your footage.
There is this weird thing where the default Frame Rate is set to 30fps. Right click sequence and interpret footage where you will change the frame rate to what you captured in camera at.
Ready to use Premiere Pro to create your edits.
In Premiere Pro, under File, select Adobe Dynamic Link, select Import After Effects Composition, find your .aep file in the browser.
It will list all the compositions in the right panel, choose your shots.
Add to timeline and edit.
You have not compressed the files (converted to jpeg or tiff), you get to use Adobe Camera Raw (same as used in Lightroom) to edit your RAW sequences/files, any changes you make in After Effects will now be reflected in your Premiere Pro project through dynamic linking and you did not need to create proxies. The best of all worlds.
This works with .NEF files as well as .DNG CinemaDNG files. With the original CinemaDNG files you keep the timecode generated by your Blackmagic Camera, Ikonoskop A-Cam dII, or Digital Bolex.