Man, I love Ghost Light, too. Right up there with Fenric. Ghost Light was just a fantastic thematic exploration on the nature of change. That, I think, is part of what makes the pacing hugely different on a lot of Seven stories, particularly the later ones; they're not straight action stories, but very allegorical and doing a great deal through implication and allusion, so they read very differently from other seasons of Who. It's fantastic storytelling, some of the best I've seen on a TV show - but what I love about it is that it's super-dense and keeps you on your toes about actively interpreting what you're watching, with a huge amount of thematic and character development. So I don't personally think it's a failure for it to reward rewatches; I think it means they're doing it right. :) (S25/S26 is, in many ways, the Sandman or Watchmen of Doctor Who, and I think, from interviews, those were actually conscious influences on how they were changing the storytelling from a straight time-travelling SF show to a much more experimentally mythic, allegorical, meta-aware/pop-culture-aware/politically-aware show.)

I would also recommend Remembrance as the gateway drug of Seven; it's sort of an homage to Who, being the anniversary episode, so it's a bit nostalgic in content and structure, and, as the first real Seven/Ace story, it's a much gentler sort of intro to the type of storytelling they ended up doing. Much as I love Ghost Light, it probably does deserve some warning labels, because it does contain a fairly high level of insanity. :)