So there's five levels of class...
What, so you're suggesting that maybe after 3rd level or so, they can choose a subclass (like Knight can either stay Knight, or go Paladin or Blackguard ((D&D thinking)) ...though that's kind of biased... maybe just more Paladin of their specific 'faith', or elemental group that they follow). Then two levels of that are available before they reach the top, then...
I 'unno.
I once had a thing... *looks for it*
It was a long time ago, sort of going on the RO system... this was way back before I started RPing, I was designing game classes...
/ Crusader
/ Paladin - Dragoon
Knight - Dk. Knight - Dk. Dragoon
Squire < Deathbringer
Hunter - Archer - Ranger
X > Bounty Hunter
Rouge - Mercenary - Assassin
Thief < / ShapeShifter - Doppleganger
Illusionist > ShadowMaster
> Sorcerer - Warlock
Magician - Wizard - Elementalist
Apprentice < > Mage
Acolyte - Cleric - Priest
Shaman - Summoner
Sage
Okay... lemme try and explain this...
Squire can go to Knight or Hunter at second level. Hunter could go to Archer or Mercenary (which are also the two classes available to a third-level Rogue). From Mercenary OR Archer, though, they can both end up as a Bounty Hunter, or the Archer could go to Ranger and the Mercenary to Assassin...
...it'd be at each level they'd pick up a number of new traits or abilities, so that the path that you take to get there can influence the end result just as much as the final level of the job that you choose...
...it's an old system based on FF or RO classes. I made it for a text-based game that I never got to making, back in like... 2002.