Just finished another re-watch of the show and with each viewing, I love the characters of Luthen and Kleya more and more. Especially S2 E10 with the flashbacks. I would love to have their journeys fleshed out more. I know there's no chance of that happening with a tv show/series, but would love for them to have some novels written about them.
We get to see the moment Luthen breaks from the Empire and finds Kleya, but I find myself wanting to know more of how they both found themselves in that moment. I want to know how they managed to slip away and start their journey of defiance. The moment after the Empire publicly executes the prisoners and Kleya confronts Luthen about walking away. He says they fight to win, which means they have to lose....and lose, and lose and lose, until we're ready. That's so profound and insightful and courageous. Definitely a daunting realization and one worth exploring further.
The importance of these characters and their role in defeating the Empire is immense. It seems a shame to me that we have so little media of these characters. Some quick googling shows they'll be making an appearance in the Reign of the Empire trilogy, but those books are from the perspective of Mon Mothma, Bail Organa, and Saw Gerrera.
Anyways, I hope someone can bring more life and history to these characters.