Well, I guess it depends of the doc you’re filming, but getting all excited by the image quality when you film a doc might not be that healthy. As long as you are able to reach a certain threshold, the return given by any improvement in image quality is trivial. If I film some people chained up to the Keystone Pipeline and being remove by the cops, with some action, I’m not sure I want the BMCC, frankly. I’ll take my Canon XH-A1, and I’m not kidding here.
Now next time I produce fiction work, then yes, I’ll put my hands on a BMCC. Content still rules. Most people who go see a doc demand to be captivated by the story and the content and the issues. They wont’ notice your depth of field and whether or not you originated the footage in 4K.