OK, I guess I'll answer my own question. The VideoPad Project (.vpj) file is essentially a script, editable in a text editor. It just isn't formatted to make it easy to use as a script lacking field identifiers and with the entire project including clips, effects, audio, subtitles all in one file. The vpj file has a checksum value included in the file as a text element at the very end. If you edit the file, obviously the checksum will fail when opening in VideoPad and VideoPad will notify you that the file may be corrupt and give you the option to proceed anyway, which you can do with no harm.
All-in-all, not easy to write a script builder with this file structure. And, like they say in all the instructional videos, don't play around with your only copy of the file!