Y'know, I want to answer those questions...
Part One: I think Cassandra not speaking, or at least being as laconic as she was during her hayday, is an integral feature and challenge of the character. The artist needs to be someone who can be suggestive and emotive to help tell the story, and seeing Cassandra quietly access a scene and use small one-word sentences to express her opinions makes her an excellent character, and a great foil for the more talkative members of the family. Even Batman seems like a windbag next to her. Someone like Tim or Jason making their snarky comments allows for some nice color commentary and dialogue tricks.
Part Two: I've got an idea: introduce Cassandra through one of the Robins' backstories, preferably Tim, Damain, or Jason. For Tim, set up an "act II" for Tim's origin (KEEP LOBDELL THE HELL AWAY!) that echoes his first miniseries from the 1990s, but replace Lady Shiva with Cassandra as his trainer. For Jason, have him have freed her from her father's tutelage shortly after his resurrection from the whole One Who Is All prophecy. For Damian, she's the weird older sister figure he remembers who he feels so we hat threatened by.
In all cases, she's being tracked by Cain and comes to Gotham for aid. After getting her Robin's support and witnessing Batman in action, she expresses a drive to follow his legacy like in her first series. She maintains contact with at least one plugged in member at all times and fights as the Black Bat, and we see her reactions to the idea of a civilian life and single minded focus on becoming one of Batman's successor's.