Personally, I don't think an all-magic character should be included in a 'weapon-fighting' game like SC, though I have no problems with someone who uses magic for some attacks while using an actual weapon. As for character ideas for possible future titles, let's see...
- Nodachi wielder: Honestly, I think Mitsurugi is getting on in age, and while I enjoy Siegfried and believe him being immortal is at least plausible due to his wielding Soul Calibur, his style seems... implausibly fast for a weapon such as a zweihander. A nodachi style would play on the Japanese swordsman and two-hander types, as a nodachi is longer than a katana, but lighter than a two-hander. Would be interesting to see, IMO.
- Demon Claw style: Has anyone here wondered what might happen if, say, Nightmare or a demon implanted one of their body parts or, more creepily, an eye into a human being? If corruption is a theme shared there, then a demonic eye implanted into a human's palm which turns it into an equally demonic claw might not be too far off. To be frank, I liked Nightmare's right-hand claw, but found the number of moves actually utilizing it lacking. Would be nice to see a character with such a claw use it as more of the weapon it could be, maybe even tentatively have whatever demonic appendage have some supernatural power of some sort. Nothing mystical, mind, just supernatural.
- Sword and chain: A short- or long-sword with a chain attached to the pommel, which has a spike or dagger attached on the end of the chain, isn't something I see in anything I've played before. Granted, the kusarigama is better suited for a chain due to being more aerodynamic, but it's been done with Kratos, yes? Not in the same sense as I'm suggesting, but still.
- A fist-fighting style that actually makes use of some darn gauntlets!: As much fun as I have with fist-fighting styles, I find it more than cringe-worthy thinking of blocking a blade of all things with my bare wrists or hands. Having a martial artist or what have you who wears an actual set of gauntlets for fighting would make better sense, yes? Good examples are Ding Feng and Meng Huo of Dynasty Warriors, and, just to satisfy my inner fanboy for it, the Dragon Bone Fist weapon from Dark Souls.
Feel free to constructively criticize my suggestions, I'm just throwing some plausible ideas out there.
Edit: As far as actual characters/ethnicities go... Koreans, Aztecs, maybe a conquistador as was suggested quite a bit on here. Hell, I wouldn't mind seeing someone peasant-like in the mix just to add some variety to the ever growing mash up of male/female supermodels and subhumans like Aeon and, in a sense, Astaroth.