Would make a great Mrs. Danvers
Every time I see her in "Downton Abbey", all I can think is that she would make a great Mrs. Danvers from Daphne du Maurier's 1938 novel "Rebecca". I find her quite scary looking in "Downton" although I can see from photographs of her in other roles (I'm not sure if I have seen anything else she has been in, though I plan to check out some that have been highly rated) that she is normally quite beautiful. Her Mrs. O'Brien looks as though she has stepped out of one of those Victorian death photographs (I had to check to make sure she hadn't been in "The Others"). Her eyes are haunting, and that hairstyle... well, I just don't have the words for it. She is brilliant in the role, and deserves all nominations and awards she receives.
I don't really see much of a need for another film version of "Rebecca" - the classic Hitchcock version with Judith Anderson as Mrs. Danvers has never been topped. However, the character makes a number of appearances (in number) in Jasper Fforde's "Thursday Next" novels. In those books, which take place in an alternate reality in which there is a "Bookworld" where books and their characters have their own separate world (it's a bit hard to explain - I recommend reading them, starting from the first, "The Eyre Affair"). Characters start their lives as blank "generics" and are trained in a similar fashion as actors are in our world, and depending on their skill are cast in their roles in various books. At some point before the action of the novels, there was an accident of sorts, and thousands of "Danvers Clones" were created. They are used as a type of army within the Bookworld and are deployed to deal with all sorts of problems. It is really quite funny, and if Fforde ever gets to film the series (he used to work in the film industry before becoming a successful author and has said that he would only release the books if he could direct them - however I think this initial position of his has evolved and so there is a possibility that someone else might make them) he would be lucky to cast Ms. Finneran in the role (and hopefully write some meatier scenes for at least one Mrs. Danvers).
In any case, in any form: a new film of Rebecca; a play of Rebecca; a mini-series of Rebecca; a film or t.v. version of "Thurday Next"; or simply a parody of the role, I nominate Siobhan Finneran for the part!