Well, this is what we seem to disagree about - I do believe that how the characters are presented in the past is important for their whole characteristic. CC's past wasn't shown just arbitrarily; it was there to provide more insight into her, to show her in broader perspective. In my opinion, if you'd create a character who is now an INTJ but he was an ESFP in the past, in wouldn't be a well-written character, because characters should develop but stay consistent. Such a character could very well be an ESFP who became kind of INTJ-ish because of his life experiences, though. That's why I think that CC is still an ENFP, even though she's become extremely cynical and detached throughout the centuries. But even if her past wasn't presented to us, I might have still had the same opinion, because I definitely do
see F in her. It's just little nuances, but it's there. Remember the episode with Sword of Akasha? Or the scene in the cave after Lelouch calls her name? It's only nuances but we see she provides emotional support for Lelouch towards the end, she prays and sheds tears for him... She comes across as very feeling at those moments. She also seemed to be very much loved by the Geass people (can't remember details anymore, sorry ^^;; ), etc. And after she loses her memories her feeling side becomes extremely clear - she behaves almost INFP/ISFJ-ish. Overall, I'd say that even though she seems pretty detached most of the time, her essense is that of a feeler.
Do you know the British series Hex, by chance? In Season 2, Ella's character is very similar to CC's (also a witch, hundreds of centuries years old, full of painful experiences...), and I have the same opinion of her.