There are some new creator types we should add, primarily for media item types (television broadcasts, films, etc.), along with accompanying terms.

• producer
• writer (as in a screenwriter)
• executive-producer
• contributor (e.g., 'Smith, Adam (with John Paul Jones)')
• narrator (as for an audiobook)

APA style would also like

• host (as for a podcast or other regular broadcast)
• guest (for a broadcast)
• principal-investigator (for a grant)
• co-investigator (for a grant)

There have also been requests before for:

• compiler
• cartographer
• performer

Alternative to many new variables

@bdarcus has rightly expressed annoyance at what are essentially type-specific forms of "author". These make writing styles more complex. An approach to streamline the complexity would be to adopt the names data model described here that includes a label field.

With that model, producer, writer, narrator, host, guest, principal-investigator, co-investigator, cartographer, and performer could all author, with a label with the appropriate term.

This could be implemented in clients by adding the appropriate term label to their CSL JSON (e.g., Zotero could add term="producer" to an author entered as Producer for a TV Broadcast item). A text field could allow users to override the label for more complex descriptions (e.g., "Guest Expert", perhaps "Principal Investigator" and "Co-Investigator").

If we did that, only contributor and executive-producer would need to be added as distinct creator types (even executive-producer could be editor (term="executive-producer"). director could be deprecated and interpreted as author (term="director")