in texmfmp.c, just add the three marked lines:

#endif /* MP */ + #if defined(pdfTeX) || defined(pdfeTeX) || defined(pdfxTeX) + { "output-format", 1, 0, 0 }, + #endif /* pdfTeX or pdfeTeX or pdfxTeX */ { 0, 0, 0, 0 } };

It overruns the initex setting, but it can be overrun by \pdfoutput (not the other way around, as it may be practical for such an option?).

I'm sorry I did not notice that --output-format was thrown out of getopt option list. I think the option is useful in some cases. I hope that the above three lines are revived. Best regards Akira