But anyway, getting back to Who and Sherlock parallels, one thing I was struck by was how Rose's relation to Mickey after she goes off adventuring kind of parallels the position John is in with Sherlock after he gets married. Spoilers for Doctor Who through (and especially for) Rise of the Cybermen/The Age of Steel, and I guess for Sherlock series three as well.
Right. So Doctor Who opens with the Doctor getting entangled with Rose while trying to save the Earth from these aliens wanting to take it over, and then Rose runs off with him to have adventures. She leaves her boyfriend, Mickey Smith, behind though he comes through on more than one occasion when they're back on Earth. He eventually goes along with the two of them in the TARDIS, though he only gets one adventure before they all crash-land into a kind of alternate reality. London but with added Zeppelins - a world where everything is just like their own London, but with things a little different. And after the main plot has run its course and the Doctor is getting ready to go back to the right reality, Mickey announces he's not going back with them. His reasoning:
What struck me about Mickey's and Rose's relationship is that by the end, they're not properly dating. Her life is with the Doctor (he asked her not to go back in the pilot and throughout the rest of it gets increasingly frustrated that she is so drawn to life on the TARDIS) and while he expects her some day to come back and settle down in London after her travelling is done, by the end he realizes as long as the Doctor will have her, she's always going to choose him. Rose, though, seems to really like the idea that Mickey is waiting for her, that he's there for her to go hang out with when she decides to go home. She likes him being there for her whenever she needs or wants him, but doesn't seem very committed to doing the same for him. And that's fine until the point when being there for her is going to cost him big - because if he stays in the alternate reality, not only is there important work to be done but his only real family, his grandmum who died a while earlier, is still alive for him to be with.
I happen to ship Sherlock and John, and Rose and Mickey clearly were involved romantically at one point, but I don't think you have to read the characters romantically to see the problem. John gets very jealous of women he perceives as being romantically involved with (Janine and Irene), there's also a line on his blog where he gets mad that Sherlock "replaced me with Molly Hooper and started solving cases" -- and while I know some people ship Molly and Sherlock, I don't see any evidence that John sees them as romantic interests the way he does Irene and Janine. But whether you see John and Sherlock as romantic or not, there's still this sense where John has this relationship with someone else that's central to his life, we see it in the opening of HLV where the script-writers give him and Mary that iconic John-Sherlock exchange of "You're not coming" --- "Then you're not going", where John has that central relationship and still wants to be friends with Sherlock but he's resentful when Sherlock seems to have other relationships in his life.
That's one heck of a convoluted sentence, so let me boil it down. John seems to want an exclusive relationship with Sherlock, but a one-sided one. John seems to want both Mary and Sherlock, but John doesn't want Sherlock to have Janine, or Irene, or even Molly. And there's something about that lack of symmetry, the "good for me but not for thee," that I don't think can ever be allowed to stand. It's like with Mickey: he's okay with the unequal relationship but only so far as it's not getting in the way of something that's better for him. It lacks the equal footing, the being fully committed to each other that true friendship (or romance if you prefer) that really binds people together. I'm not even sure it counts as a real friendship if you're willing to let someone give you something good but hold back from giving it back to them in kind. It seems to lack reciprocality, which seems key to a good relationship. I'm not saying that John has to divorce his wife and start up a romance with Sherlock, or that they should have a platonic but exclusive relationship, or whatever else. But if there's anything the Rose/Mickey relationship seems to teach, it's that that kind of disconnect, where both people aren't committed to each other in the same way, just can't work longterm.
Or maybe I'm babbling. Still stuck in head-cold land which makes everything seem to make sense until the moment I try to explain it. Ah, well. Thought other people might find the connection interesting anyway.