I know most of the discussion has been on whether Meryl will voice Aslan, and some others have suggested she'd be better for Aunt Letty (which I agree with), but what other options might exist? Bear in mind that Greta seems to be adding in a lot of material that isn't from the book.

Here is one idea i had:

* Meryl plays Jadis's mother in flashbacks showing the rivalry between Jadis and her sister. Perhaps the mother warns Jadis and, later, when she encounters Aslan, she hears her mother's voice, not what he is saying. (I came up with this idea when trying to get my head around the fact that Meryl was in discussion to voice Aslan).

Another option could be she plays Polly's mother (on face value, she would appear too old, but it does appear Polly's family are going to play some part in the film).

Or, it might just be a cameo, as a shop-keeper when Jadis goes on her London rampage -- something which, thankfully, we know is going to feature in the film.