Now, the point to all this blustering about qualifications is to get at something the Grand Moff said a while ago:
“It’s just a question of who credibly is going to agree to go in the TARDIS? Who’s going to do it? Is it going to be a mother of 15 children? No. Is it going to be someone in their 60s? No. Is there going to be a particular age range? I mean… who’s going to have a crush on the Doctor? You know, come on! It’s more than a format. It’s evolved from good, dramatic reasons.”
With respect to Moffat, and with pains to point out that he is an award-winning screenwriter and I am not: bullshit. For one, the Sixth Doctor’s run with sixtyish history professor Evelyn Smythe is one of Big Finish’s real triumphs, a perfectly tuned relationship that works precisely because of Dr Smythe’s age and rich life experience.
And why not a mother of 15 children? Because she has responsibilities towards them? The Doctor has a time machine! She can kiss them goodnight, be off adventuring for as long as she likes, and be back before any of them so much as turn over in bed! Martha Jones’ arc explored this! For heaven’s sake, Moffat himself spent large swaths of series 5 doing the same!
I’m not really sure how to parse Moffat’s comment about companions having crushes on the Doctor, but I do want to stipulate that this trend of everybody falling in love with the Doctor is one of my least favorite aspects of the new series.
In short, I think that the very best thing Moffat could do for the show would be to write down all the requirements he thinks a companion should have, and then deliberately scribble them out and write a companion that violates as many of his requirements as possible. Because fuck “the rules”. Because adventures are for everybody, or they should be, and it breaks my heart to see the Doctor, of all people–a trickster figure uniquely qualified to break rules–endlessly select from the tiny subset of society that is young, well-off, abled, cisgender, pretty white British women.