Not sure how far you are into your ideas for this @Kexikus, but you had wondered about some ideas regarding Quatra (spelling?) and the easiest answer for Revan finding out is simple I think. Just have her walking around the enclave, or speaking to the other masters, Revan could overhear her talking, and then relay what she or he overhears to Juhani who grows increasingly angry over Quatra's betrayal. See lightside Juhani takes it in an accepting manner, now if I were in her boots, I would be p***ed off, very, very hurt to the point of wanting to kill her all over again, and darkside Revan can pull her further into the darkside.
Does that sound like a good idea? I mean you have a fragile, vulnerable girl whose upset and you pull her further, further into the darkness, makes for a very good story. Then there could be a larger confrontation at a later date. Juhani strikes me, a lot like Jaesa, eager to trust someone, needing family, wanting to love and trust people. And I think reading between the lines that Quatra took advantage of that majorly. As for a character design for her, why not simply give her one of the head designs for one of the female player characters that way you will save yourself some extra work?
PS: I *LOVE* the idea for this mod, and I've got a cute Juhani reskin by Nimduril, any chance there could be a patch for it at some point?