I loved her design, she was a beautiful idea, with one of the most graceful fighting styles, and her lack of use in Tekken games is extremely disappointing.
If we can have the one hundred percent identical characters Eddy and Christie, or even the slot shared Panda/ Kuma (I love you Panda!!), then we can certainly have a character with a VARIANT of the Manji style. I never saw Kuni to be too much like Yoshi, especially with how different she was in Tag. She was no less diverse than Anna was from Nina.
Honestly, the ONLY gripe that I have with Tekken 6 happens to be Kuni's absence. When I play it, it just feels like something's lacking. That's certainly her.