I've made a converter that converts FamiTracker text exported files to IT tracker modules.
Currently it's able to properly convert FTM patterns into IT patterns, but playing is currently limited to standard NES 2A03 pulse and triangle channels only.
You could convert a NSF file to FTM by NSF Importer
and then using FamiTracker's text export feature to generate text file.
Windows binary here: https://www.dropbox.com/s/yq3yhx864yj3asa/ftmtxt2seq.zip?dl=0
Sources available here: https://github.com/Mistranger/ftmtxt2seq
(use CMake to make an executable from them)
Usage: drag-and-drop FTM text exported file to .exe (or read in-program usage info how to use it)
Example of result IT file: https://www.dropbox.com/s/mcmuurjyprt3j ... ck.it?dl=0
(from Digger T. Rock)
I still don't know how to properly convert noise channel without overloading IT file with bunch of noise samples, same goes to DPCM samples as well, so I would listen to your suggestions of how to implements these features properly.