Bring on the tough stuff - there’s not just one right answer.
Imagine that you could rewrite this novel in the first person. Which character would you pick to tell the story? Who would make a good narrator? Who would make a fun unreliable narrator? Is there a character who would be totally unsuited to being a narrator, no matter what? Why?
Your funding finally came though, and now you can fulfill your dream of turning this novel into a mixtape. (You are a visionary!) What kind of music does each character get? Who gets turned into an opera aria? Classic rock? Jazz? A cappella? Gregorian chant? Heavy metal? Gangsta rap? Why?
This is a crazily long novel. Imagine having to make a bunch of short stories out of it. Which parts of the plot could be extracted to make a good short story? Which can't exist outside the giant narrative? What details would you have to cut out? Would something be lost? Would something be gained? What does that say about these sections of the novel? What does it say about how novels are different from shorter pieces of prose?
The novel is split into two parts. Are there other ways to divide it? How/where would you split it into three, for instance? Into four?
Write some dialogue between characters who don't ever meet in the actual novel. How would Dorrit and Miss Wade interact, for instance? Tattycoram and Amy? Old Nandy and Frederick Dorrit? Mrs. Gowan and Mrs. Clennam? Are there some characters who seem like they would hit it off? Any that would just immediately want to kill each other? Any that would not be able to find anything at all to talk about?