You probably know this and may have thought it through and dismissed this,
but a Kogan book on this whole story* would be both interesting (obviously)
and very pitchable -- you'd probably have to shape into a bogus journalistic
"narrative" at the time of the pitch ("how a new kind of women's singing
found the light and lost it again and found it again", or whatever), but
this could be junked or complicated beyond recognition in the book itself

*ie a book to explain to ashlee why she should trace her ancestry back to
baez, by detailing same

i'd actually really like to see a book that ran this story in parallel to
the tales of the rise, tribulations, oedipal splintering and etc of the
various waves and factions in feminism (political ratyher than academic),
but that may not appeal to you so much! though i think you'd do it very well