I'm talking about Final Fantasy 2, 7, 8, 12 where everyone is a general character that can pretty much learn every spell/skill there is (in other words Super Mages). I find some are hard to simulate while others are easy (BW, WW). Here's what I do.

FF2:
Black mage - all black magic/daggers
White mage - all white magic/staves
Knight - swords/heavy armor
Thieft - daggers/almost every piece of armor is heavy so no choice there

FF7:
Black mage - all attack materia/back row
White mage - all curative materia/back row
Monk - counter materia (Tifa really suites this one)
Thief - steal materia
Ninja - throw materia
Knight - cover materia
Summoner - all summon materia/back row
Blue mage - enemy skill materia/sense materia

FF8:
Thief - mug/initiative
Knight - cover/mad rush
Dark Knight - darkside/absorb
Summoner - only person with gf command
Black mage - only draw attack magic
White mage - only draw curative magic
Red mage - only draw basic attack/curative magic, no -agas or other high-level spells
Monk - counter
Time mage/Oracle/whatever - only draw effect magic/lvl up/lvl down
Chemist - med lv up/auto-potion/treatment/revive/recover/move-find

FF12
Knight - swords/heavy armor
Thief - steal/daggers/light armor
White mage - white magic/staves/mystic armor
Black mage - black magic/rods/daggers/mystic armor
Red mage - white black magic (only up til lvl 3)/swords/mystic armor
Dark Knight - swords/heavy armor/souleater
Ranger - gun/light armor
Archer - bows/light armor
Dragoon (wannabe) - lances/heavy armor (but no jump command)
Summoner - rods/mystic armor/summons exclusive to that character
Paladin - swords/heavy armor and white magic until lvl 3