She is a human actress, though, with prosthetics on. So, it's not like I'm grabbing a cartoon character, which is the only thing the guidelines have rules against. See. Also, Vastra interacts in regular human society most of the time... with creative veil placement. There could be workarounds, if necessary. Our limits are not against inhuman characters, but against inhumanoid "toons" her form is still humanoid enough. She's not like... a dog I'm trying to make a human form, you know?
And yes, I know. I'd have to think about it. Amy would be extremely tempting, though. Donna, too. Hrm.