There's been rumors of a remake of VI. I for one don't take them to be particularly serious or likely, but it's a fun concept. And, since it's fun to do, I'd like to see who people would pick to be the voice actors for the various characters. You may do Japanese, American, or both at your perogative. You can go with established game and anime voice actors, or you can use popular stars and actors. I don't really care, just give me a reason why you picked them.

Terra: Paku Romi. Paku Romi does a lot of young boys, such as Edward Elric from Fullmetal Alchemist and Hitsugaya Toushiro from Bleach. However, hearing her sing, it's readily apparent that she has a powerful feminine voice, and I'd love to see her in the role of Terra, especially given how Terra develops as a character over the course of the series.
Celes: Maaya Sakamoto. She does a lot of voice acting and her singing is absolutely wonderful. Celes is the one who sings at the opera, and it absolutely must be sung by Maaya Sakamoto. As an additional note, Maaya Sakamoto voiced Aeris, among other notable roles such as her very first, Hitomi, from Escaflowne.
Edgar: Takehito Koyasu. He's got a nice deep voice, and he can do arrogant rather well. The amount of roles he's played in are absolutely staggering, and he'd make an excellent voice actor. Koyasu voiced Seifer in Kingdom Hearts II, but he's done other roles that would probably be more appropriate to Edgar, such as Hotohori from Fushigi Yuugi.
Locke: Hikaru Midorikawa. He's got a good repetoire of both heroic and villain voices, and I think he'd do a good job as Locke. He's done roles such as Zelgadis from Slayers, Heero from Gundam, and Marth from Smash Brothers.
Sabin: Nobuyuki Hiyama. He's done several roles with a rather powerful voice, such as Siegfried/Nightmare in Soul Calibur and Shougo Asagi in Tsubasa Chronicle. He can definitely pull off the "tough guy" voice.
Cyan: Noriaka Sugiyama. Currently a fairly new voice actor, he's done both Uchiha Sasuke from Naruto and Ishida Uryuu from Bleach. Both of whom end up being very emo. I'd say he fits the bill.
Gau: Miyu Irino. Miyu Irino does a lot of younger boys, and was the star of Kingdom Hearts, giving voice to Sora. He's also done some other roles, generally in the same age group such as Syaoran from Tsubasa Chronicle and Haku from Spirited Away. It'd be amusing to see him do some of Gau's more notable parts.
Setzer: Ryotaro Okiayu. Because he already is (see Kingdom Hearts II).
Mog: Ikue Otani. She's the voice of Pikachu. Thus, she voices the random cute thing.
Shadow:
Strago: Tomokazu Seki. He's done many different roles before, and it'd be interesting to see him play the role of an older man, since he's often able to play fairly humorous roles. A few past roles are Van Fanel from Escaflowne and Kyo Sohma from Fruits Basket.
Relm: Hayashibara Megumi. If you've seen Slayers, you'll know that she has no problems playing the bratty little girl.
Umaro:
Gogo:
General Leo:
Emperor Gestahl:
Cid:
Kefka: Kôichi Yamadera. He's done many, many roles, but the main one I'm basing this selection off is Albedo from Xenosaga, a villain possibly even crazier than Kefka. Yes, Kefka is one crazy bastard, but he didn't cut off his own head.

Obviously I don't have one for everyone, but I got MOST of the major characters. So who would you pick?