This was what I went with.
Vaan - Knight/Archer - Knight for his power ability to tank, and gives access to white magic to take advantage of his magic stat. Archer gives range if needed and access to light armor.
Ashe - W.Mage/Bushi - Bushido provides good speedy attack with her atk and mag stats, whilst white mage provides healing and access to support magic. Unfortunately it means she only has access to mystic armor, but since she's only going to be attacking up close in speed, she doesn't need great defence, just to be able to jump in quick when needed and jump back out for support.
Penelo - B. Mage/Monk - Best magic user for Black Magic on attack, and Monk gives access to higher level white magic as well Light Armor. Since she's a ranged fighter she doesn't need heavy armor.
Balthier - Shikari/Uhlan - Shikari to take advantage of his speed and light armor, Uhlan provides aerial attack with spears (second fastest attacking weapon) and heavy armor for protection since he'll be close range.
Basch - Foebreaker/T.B. Mage - Foebreaker for sheer power to tank and heavy armor, and TB Mage for support.
Fran - Machinist/R.B. Mage - Secondary magic user for the weakest character in general, and machinist gun doesn't rely on stats for attack which works to her advantage.