So I wanted to throw this character out here as I think she can work. Judging from the cast built up so far, she would be the only true imperial of her kind which I think makes it an interesting pick.  This is merely a concept at this point as I could not be bothered to turn four pages of lore into a manageable character sheet at 1am.

[b]Lady Karra Ciph: [i]Apprentice of the Sith[/i][/b]
Karra is not her name, not by birth at least. It is an identity she took on when she was effectively adopted by none other than Lord Vader. Before the war, before the Republic was thrown into chaos by the threat of separatists, she and her family ran a small starport in the outer rim. However, [b]all good things must come to an end.[/b] She was never a malicious child. She was young and playful and a tinkerer but none of that would matter to the Karazak slavers that shot her father and took her, her mother, and the rest of the town wholesale. The republic outpost a stone’s throw away was none the wiser. [b]She was ten years old.[/b] She never knew of the war that raged, of the complete destruction of the republic, until after. She hardly even noticed that she had been touched by the Force.
The Empire noticed however. It was not a Jedi that freed her from bondage, it was an inquisitor of the Empire. As a child she saw the Jedi as great and noble protectors, but years of menial work for little food, being sold from owner to owner and ripped from what family she had left, had beaten the youthful optimism from her. The Jedi had failed her in her time of greatest need. [i]The Jedi were incompetent; the Republic in all its talk of justice and peace was a sham,[/i] so she convinced herself. No tears were shed upon learning of both their fates.
The tragedy of the past turned her readily towards the dark side. When she was brought in, Darth Vader himself seemed to take a personal interest in the child. She was given a more extensive training than any inquisitor before her. She was taught to craft her own lightsabers in lieu of a traditional inquisitor’s weapon – forging a twin set joinable at the base. She studied first a double-bladed staff style of fighting, and later focusing more on separate dual wield. She learned to harness the Force with more strength and power than any inquisitor. She however could never truly quiet her mind enough to be precise with her Force powers. Her own uncertainties impeded her far too greatly.
Vader had become a shred of a father figure to her. Perhaps this was simply an adolescent child and the product of tragedy latching onto the first person who seemed to care about her. Whatever the truth, she received great preference over the rest of the Inquisitorious, and had the clout to pull Vader’s rank as if it was her own. Yet despite being trained as a true apprentice of the Sith, she was an inquisitor in rank still. Her training was kept secret from Sheev, who would certainly have her killed if he knew. He already had growing concerns about the Inquisitorious as a whole. She never knew that not long before the destruction of the second Death Star, Palpatine had learned of her training. If Luke Skywalker had indeed been converted to the dark side, she would be cast aside – potentially killed – to make way for this new apprentice. She was far from Endor when her master was killed.
Vader’s death gave her drive, conviction, purpose. These were all qualities she lacked previous. Her loyalty to Vader made up for this but in absence of a master, she was lost. The confused little girl she had always been was oncemore who she was even at the age of 37. Everything she knew was coming apart at the seams. She heard of the rebel incursion on Endor and hurried back as fast as the hyperdrive would carry her and her ship. Yet she was too late, and all that was left was a debris field.

Interestingly enough, she very much parallels Asajj Ventress in her story and her character arc. Also, [b]yes[/b] this is what I considered “manageable”.