A character that I would love for Lucasfilm to explore is General Grievous. Yea, I know we get a lot of him in STAR WARS: THE CLONE WARS and we have his appearance in REVENGE OF THE SITH (not to mention the Legends brand stories), but I would love to know more about Grievous before he fought in the Clone War.
We know a little about Grievous, thanks to the small bits we get in the television series THE CLONE WARS. We learned that at some point in his past, he chose to have cybernetic upgrades done to his body. This results in the cyborg that we see in THE CLONE WARS and REVENGE OF THE SITH. In season 1 of THE CLONE WARS, we visit the General's lair. Inside his home, we see statues of Grievous in his former state. We see him as a normal Kaleesh (his species). Then we see a statue of him with cybernetic arms, and another statue of him with cybernetic arms and legs. So it seems that he had these upgrades at different stages in his life, and not all at once.
Why did Grievous chose to have himself mutilated and turned into a cyborg? The answer can be found in the LAIR OF GRIEVOUS featurette from season 1 of THE CLONE WARS. In this featurette, Dave Filoni, Supervising Director of the television series, and Henry Gilroy, Story Editor for the series, said the following on Grievous' backstory:
"One of the things that George had mentioned was that he had really wanted to be a Jedi" -Dave Filoni
"But he wasn't Force-sensitive. He wasn't able to use the Force. He knew he could never be a Sith Lord." - Henry Gilroy
"And his rejection of Jedi status drove him to have modifications done to his body." - Dave Filoni
You can watch the featurette to LAIR OF GRIEVOUS
I would love to see a comic book series or novel about a younger Grievous struggling with this rejection of Jedi status, and his willingness to mutilate his own body in order to make himself strong, quick, and powerful like the Jedi.