I managed to let RNJ work with RTW 1.5 (no BI 1.6, no RTW Gold).
You need to create an empty BI file within your RTW file, to put the Shogun2 file within the BI file (you can put the rest of the RNJ2 file in the Shogun2 file) and to change the three data files below.
You can play the campaign through the provincial campaign.
I don't manage to play the campaign through the main campaign or to play a custom battle. Help is welcome.
Norton doesn't allow me to download the 2.6 and 2.8 patches. Does anyone have them in a zip file or another file that is not deleted by Norton?