Who should be a guest fighter in Soul Calibur 6?

Mortal Kombat characters:

Shang Tsung - It would make sense more than most MK characters, what with Tsung being immortal and all, so time travel stories are unneeded. He is a good swordsman in his series too, and his design would fit in extremely well overall.

Scorpion - This is the one that would most likely get in over all other MK characters, because Ed Boon likes Hanzo the most. Nonetheless, Scorpion could also fit in quite well, especially if he were to wear his more armoured costumes from the 3D games that actually looked pretty badass. Story? After forsaking the undead Earthrealm champions, the now corrupted Raiden uses the Shirai Ryu as his personal law enforcers. After Scorpion and his clan fail to invade Outworld, Raiden magically sends them away to the Soul Calibur universe.

Kitana - The princess of Edenia would be a nice fit in the Soul Calibur universe. She wields a very unique weapon, and, like Shang, doesn't need a crappy time travel explanation as to how she could land in Europe in the 17th/18th/whatever century. 

Street Fighter characters:

Ryu - The main character, so he'd be likely to get in over other SF characters. This could continue the saga of Ryu showing up in different games as a guest. Story? Ryu gets stuck in an interdimensional portal, and ends up in Soul Calibur. The end.

Gill - The final boss of Street Fighter III would be a good fit for Soul Calibur. He could create short swords made of fire and ice as weapons. Plus, it would also be cool to see him face off against Algol. Story? Gill and the Illuminati create an interdimensional portal to the Soul Calibur universe. Gill, believing that the place on the other side will be heaven or the Promised Land, boldly steps through.

Twelve - The weirdo from 3rd Strike would also be a great fit, since the thing can transform his arms into different weapons. He would be different from the numerous other ditto fighters from SC, since he can transform into his opponent in the heat of battle. Story? Urien witnesses his brother step inside a portal to the universe of souls and swords. He and his mindless soldiers launch an ambush on the Illuminati while they are in the middle of the experiment. During the chaos, Twelve falls through the portal after Gill.

Let's be fair though, Namco would probably tease a character who would fit in really well like the ones we mentioned above, and then put in Lieutenant Columbo and the Fail Whale. I mean, let's face it, Ezio and Heihachi (the latter by virtue of already being a fighting game character owned by Namco) have been the only guest characters to really fit in so far. Not that Star Wars characters showing up in 4 was a bad thing, in my opinion. \^o^/