But due the number of C NTS functions used in Geany
Have you actually checked how many functions used in Geany would be affected? I haven't, but I ask because it might be worth actually checking to see, maybe it's not so many more as one might assume.
As for editing it, I have yet to see a real use-case for editing such files in a text editor/IDE
The obvious one that comes to mind is actually fixing the file by removing the NUL, which IIRC Scintilla helpfully displays using a special little icon/glyph.