Love JR, but I think CF has done a wonderful job and I don't think JR can be better than CF.

Foy won the Golden Globe. 'nuff said.

I did watch all of Partners, but not because of Raine. I enjoyed her on Call the Midwife, but I certainly would not rate her as a "brilliant" actor, just "adequate."

I barely got through one ep of Partners in Crime. Sorry, but I agree with Cakesandale. Have you seen the earlier version of Tommy and Tuppence? Granted, Francesca Annis is a tough act to follow, but Raine? Meh.

I thought Jessica Raine was great in Partners in Crime and she had excellent reviews for her role as Jane Rochford in Wolf Hall. She is a very versatile actor.

By your criteria, Raines would be better suited to play Margaret (if she could act). Although she doesn't look much like her, she does have something in common with her: being a husband-stealing homewrecker.

Sorry, but I find her very bland and not a very good actress. Call the Midwife got a lot better after she left. Foy has been nominated for a Bafta for her superb performance as Anne Boleyn in Wolf Hall. Imo she looks more like QEII than Raines.

She looks no more like Elizabeth than Claire does. Claire already does a fantastic job, in the role. She has Elizabeth's very prim speaking voice down to a T.
There really isn't going to be an actress who looks overwhelmingly like Elizabeth. The royal family have pretty distinct looks (owing somewhat to how the branches of their family tree are quite tangled) that you aren't likely to find those exact features in any actors who've made a career for themselves. They're not considered very beautiful features by modern standards, and there aren't many young, female character (re: less attractive, by Hollywood standards) actors available.