@JonathanG: After I wrote my post, I later thought about Daisy's type, and I did think about ISFP, and I think you're right. She doesn't seem terribly extroverted. I do see Fi in her. But then she gets oddly stubborn about how she wants things to be--like not marrying William and wanting more recognition from Mrs Patmore--that seems tert-Ni. I think you're right. I'm not too familiar with Type Six, even though that's my head fix, but she definitely does seem to be anxious like a Type Six, and she's not a wing 5. I don't really see much of a Type Two in her, though...
And yay, I got O'Brien right! Yep, I think she's definitely in some kind of Si-Fi loop in season two.
Also (and this is for anyone to freely answer), what about these characters, even though we haven't seen much of them? I have a few guesses (just MBTI--I'm not good enough yet at doing Enneagram types :P ):
Gwen - INFx (I may be terribly biased here, though, because she's one of my favourite characters and I wish she came back to show off her secretarial skillz! ;D )
Aunt Rosamund - ESTJ (she freaks me out. I feel like she constantly has something up her sleeve, like some hidden agenda or something)
Mrs Patmore - ESxJ (she has this bossy Je-ness about her, but I can't tell whether it's with T or F! ;D )
Ethel - ESFP
Lavinia - IxFx
Sir Richard - ENTJ