I have no idea how much influence the showrunner has over the episodes and the writing. I know that some showrunners insist on controlling every detail, right down to things like costumes and sets. I don't think Kripke was that way and I don't see Gamble being that dedicated either and frankly, I wouldn't want her to be. Her contributions to the show (such as I'm aware of them) haven't exactly blown me away and I don't see her revitalizing the show with an exciting new creative vision.