Boskonovitch (SPOILER)died in Tekken 5. Kunimitsu was in Tag Team and Tekken 2. Gon wasn't a serious character, he wasn't even original. He was from a manga in Japan.

EDIT: Kunimitsu was probably removed due to her uselessness. She was almost the exact same thing as Yoshimitsu, only she weilded Kunai (I think) and was a girl. I still liked using her, though.