Hm. The script was more for turning existing Inform 6 game files into a web site, without using all of I7.
It’s hard to replicate everything I7 does without parsing the I7 source code. The answer here may be to run ifsitegen.py once and copy the necessary .js files over into the directory that I7 builds. Or go back to the older blorbtool.py solution that’s on the wiki page… I apologize if this has led you down a garden path!