Let's start with what we have, for absolutely certain:
Code:
Siegfried Zasalamel Nightmare
Xianghua Maxi Sophitia Ivy
Yoshimitsu Kilik Grøh
Mitsurugi Geralt Taki
Random
I see these slots as non-negotiable, personally:
Code:
Siegfried Zasalamel Nightmare Lizardman
Xianghua Maxi Sophitia Astaroth Ivy
Yoshimitsu Kilik Inferno Grøh Voldo
Mitsurugi Geralt Taki Cervantes
Wizardman Random
Astaroth and Voldo, I feel like we've all kinda agreed that that's where they're going to go. Lizardman, if included, which seems like he really will be, should ride with the Schwarzwind square in the upper right corner. Inferno and Wizardman being important plot-central characters and unlockables, in all likelihood, puts them in the center. Inferno being in the center of everything also carries great symbolism. Cervantes only has two spots left on the "evil" side, and vertically opposite his daughter makes more sense than otherwise.
We still have Seong Mi-na, Talim, and Tira to place among these slots, and Tira only really has one possible spot, that being below Taki, considering that's the only "evil" slot left. Though Seong Mi-na is pursuing Soul Edge, this means she has to be somewhere on the left, but opposing Tira just doesn't seem right. I don't even really think she qualifies at having a rival among any known characters, which is why I put her in the lower left corner. Same goes for Talim, who could go in the center, like Zasalamel, but she's just not important enough to the plot which seems to be what the center pillar is all about, so the only really other logical spot for her is below Yoshimitsu.
That leaves speculation, and why I feel like the other two characters are Hwang and Raphael. Hwang works to oppose Lizardman, since they shared a stage in SoulCalibur, and he also fits right in with the "heroes" section of the board, since he replaced Xianghua for Korean versions of the game, so being right next to her makes a good deal of sense. And Raphael and Tira were in opposition in the SoulCalibur III title movie, so their "rivalry" has somewhat a precedent, though that's kinda weak, I'll admit, it's at least something. So this is why I believe the final result has to be:
Code:
Hwang Siegfried Zasalamel Nightmare Lizardman
Xianghua Maxi Sophitia Astaroth Ivy
Yoshimitsu Kilik Inferno Grøh Voldo
Talim Mitsurugi Geralt Taki Cervantes
Seong Mi-na Raphael Wizardman Tira Random