Perhaps for Beauty and the Beast, I could add more interaction between Belle and her sisters. That is something that was a bit lacking, because they lived together in the end, but I am not sure about their relationship prior to her marrying a prince. Like many stories, the sisters might get jealous and try to kill her.
(Three friends. Web Source.)
In the Language of Animals, Jack's story was quite interesting with his travels and learning to understand animal language. I can go in depth with his schooling or his friend who admires him. In his schooling, his teacher could have an all-knowing animal. So, instead of learning from the teacher, he learns from the teacher's pet. And in Jack's story, he always has a friend. I can write about his friend boasting about Jack at a bar or something. Because he is with Jack, he might even learn a thing or two.
I have not read about a giant before. Perhaps I can add that character to a story. In A Dozen At a Blow, I am not quite sure if I like the main character. Although he is witty, he is cheating. With his wits, I could even insert him into one of the other stories. He can travel with Jack in the Language of Animals.
Another story I could write about is the cat's background in The Earl of Cattenborough. Since the cat did all the talking and thinking, I wonder if they liked the cat or John/Jack.
Bibliography. Europa's Fairy Book by Joseph Jacobs; link to reading online.