I don't have an answer for you (other than google finds a couple useful posts from KLOV).
I would like to add a question.
How do you get the Self Test menu to show the additional debug menu options?
I've been modifying the vegas driver in mame for real 49-way support, at one point I got the self test menu to add 5-6 items for extended debugging. The control test menu was particularly interesting as it output the memory byte for each input location (4 iirc).
Rebooted the machine and haven't been able to get back into it.