Here are my suggestions:
Daphne: She is from a pureblood family and could bring about more seats on the Wizengamot. She is supposed to be cold and distant, but that could just be a facade waiting to be melted.
Gabrielle: she has always been subservient to Harry, I think she would make a good understudy for Tonks.
Susan Bones: She is loyal. Remember in the movies she was the only one at the Hufflepuff table in the library who stood up for Harry when Justin, or whoever that was, began saying that Harry was the Heir of Slytherin.
Pansy: maybe. If she was broken by the loss of Draco she could be a decent add in. Kind of a case for him to save.