Now that Zotero offers a "Book Author" for "Book Section", it would make sense to map this field to 'bookauthor' for BibTeX import/export. Traditional BibTeX doesn't offer this, but biblatex does, and I see only positive effects in supporting this: Traditional BibTeX styles will simply ignore this field, so there is nor harm on this side, but for biblatex users data exchange would definitely improve a lot. (Originally, the bookauthor field was one of the main reasons I switched to biblatex, because it's quite common in humanities but isn't supported by traditional BibTeX).