And I think an approach similar to what Roth articulates above could work, focusing on the emotional facts and feelings of what the Manson murders were and what they did to our psyche as Americans. And I think that's an approach Tarantino could achieve, and it would really be something. I can also see him, so interested in shifting timelines and the past colliding with the present, riffing on this idea from Joan Didion's essay The White Album, about how the Manson murders became this story we tell ourselves, this folklore that lacks clarity:
Now that I think about it, an approach similar to James Cox's WONDERLAND, where Val Kilmer plays John Holmes and tells the story of the Wonderland Murders, but through a variety of differing perspectives, with the actors taking on different approaches depending on who's telling the story. (REVERSAL OF FORTUNE and ALPHA DOG both do this as well.)
And, of course, Didion brings up the other great quote from that essay that's in Tarantino's wheelhouse, too:
Hunter S. Thompon's Wave Speech comes to my mind reading what you've posted here.