Okay, I feel like an alien sloth turtle at the moment, so this is going to be brief.
Direction, at least to me, feels like a piece that's very limited by the programming ability of the team, tied directly to their ability to make sense of everything that goes on in those incoherent walls of code. That said, my programming ability is limited, so I may be incorrect.
Secondly, I don't agree with Palas' statement regarding screenwriters. While the screenwriters certainly do write stuff, in movies the text isn't the primary method with which the audience is engaged. The text is front and center in a visual novel, and this turns it into the pillar holding the other areas together. A draft stunning in a word document can go anywhere from adequate to drivel as a direct port into a VN, and so as a writer it's absolutely necessary to edit the text as much as possible, even more so than standard writing. You're going to be fiddling around with those sentences long after they've been place in - before, during and even after the setting of the scene's direction.