The main issue with building characters from RPGs is that they level differently from Pathfinder, but given my name and obvious specialty, lets give this a shot...
Cloud
Spoiler:
Mostly fighter, with limit breaks indicating some kind of magical aptitude, so leaning towards fighter/magus. Stunning Critical (due to cross slash), and perhaps some kind of homebrew spell to replicate blade beam? Omnislash is an interesting one to work out too. Meteorain seems to be some fluff on a fireball spell. Braver and Climhazzard seem to indicate a Vital Strike feel too. Thus, perhaps going barbarian rather than fighter in order to gain pounce and furious finish. Obviously not min/maxed, but that's how it seems to go. High strength and decent con, but as his stats are higher than almost anyone else overall, i'd say he's a 25pt buy over everyone else's 15. Charisma dump stat.
Barret
Spoiler:
Gunslinger predominantly, but a few of his weapons are melee, along with Hammerblow. Perhaps some kind of trait to explain his gunarm. High constitution, as his stats are relatively based on defense in game, but low charisma, unless Mr. T is charismatic as well.
Tifa
Spoiler:
Monk, with some grappling involved. medium strength, high charisma.
Aerith
Spoiler:
As the predominant healer that dies relatively early in the game, a low constitution cleric seems to be the way to go. Quarterstaff maybe?
Cid
Spoiler:
As a spear wielding high damage character, most would go fighter or rogue. However, as captain of the Highwind, he's a pilot. Thus, you could reasonably argue he's some variant of rogue (driver) or (pilot). Also, a couple of levels of alchemist to explain Dynamite (limit break, damage to all enemies).
Cait Sith
Spoiler:
Druid animal companion. He's a construct, easily replaceable, and has some pretty cool limit breaks that you can't reasonably replicate in game. Reeve (druid himself) wouldn't be involved.
Red XIII
Spoiler:
A difficult one. I'm inclined to agree with Byrdology on this one.
Yuffie
Spoiler:
She's a freakin' ninja. But she's also a thief. Rogue much? Shurikens and a Starknife for flavour. OR a starknife with the returning property.
Vincent
Spoiler:
The most difficult of the lot. He's immortal, so he's an elf. But he also contains Chaos, a sub-weapon, and can utilise his form, among others. It's a tough one, because he would most likely be classed as a gunslinger for play reasons only, but he also transforms. I would really put him as some kind of caster with a transformation ability and some gun aptitude. Or, you know, as an Alchemist into Master Chymist, for the alter ego. In game, you don't control the transformed Vincent, so the idea of him not being in control is a strong one. Also, his ultimate weapon is a difficult one to replicate in game. Perhaps damage increasing with level? or a tally kept of enemies killed, but that's just not pick-up-and-play.
Sephiroth
Spoiler:
Magic items abound. He flies, he's a master swordsman, he sounds like magus into eldritch knight to me.
