I do really like Alice Krige, I think she'd be better as Julia/Natalie than Liz/Naomi, but I wouldn't object to her in either part.
I love Juliet Landeau, I'd love to see her in some part. She'd make a very interesting Julia, not sure if she's old enough to be Josette's aunt Natalie if tptb have her in that role too. She may be older than I think, and Natalie could always be a young aunt, closer in age to Josette than Andre. It would hardly be the strangest family relationship in DS.