Fascinating stuff! I often forget how lucky we are nowadays that both RTD and Moffat are massive fans of the show, have such passion for it and actually want the job! I remember reading as far back as Troughton's time there were producers who didn't really want to work on Doctor Who and only did so because the BBC would promise to move them onto something else after they had done their time.
It will be a sad day when Moffat decides to leave (not that he seems to have any plans to fortunately) because I don't really see anyone else of the same calibre who would take over.
JNT did love the show, but he said in retrospect, he should have just resigned after the 20th Anniversary. He was holding out for a new gig, initially his pitch for Impact, but neither materialised for him, sadly.