Some new guy? Come on. Ancient Ogre fits perfectly as the opposite of Gil.
And as for Oni, he can be the opposite of T.O., Jinpachi, Unknown or even Azazel. Tekken is in no short supply of godlike monsters.
Other than that, the list looks great. Some of the matchups aren't exactly what I would've envisioned, but I know it's not easy to give everyone an ideal partner in casts this diverse, so I understand.
Vroom Vroooom! FULL AUTO!!! http://www.gamefaqs.com/boards/652997-tekken-tag-tournament-2/63435382