Just some stuff to point out for you all. You can't change back to the orignal classes, at least in what I can see. And the super special classes (assassin, zen master, valkrie) I think their can be only one unless you restart the game. I only know the quest for the assassian not the others.
The warlock. you get access to the Moon and Fiend and can still trian in the previous spell books that you had.
Also once you are a class and you change you can't go back. And yes you can start a class join the new guilds then cancel. In fact all 6 of my new party (just restarted) are all members of the 3 guilds at the 1st town.
As far as what I have planned is this
Colbey: Human -> Warrior-Barbaian-Pal-Ninja-Samuri
Freya: Elf-> Warrior-Barbaian-Ninja-Pal-Valkrie
Piccolo: Lizard -> Warrior-Barbian-Pal-Ninja-Monk-Zen Master
Daloi: Ratling -> Warrior-Barbian-Pal-Monk-Ninja-Assassian
Aphrikelle: Pixie -> Priest-Paladin-Barbaian-Samuri-Warlock-?
Gandolg: Oomaz -> Wizard-Pal-Ranger-Bard(?)-Warlock
Guild of three swords in in the armory holds
Barbian, Ranger,Samuri,Ninja,Paladin
Guild of shadow is in Pawn Shop holds
Ninja, Bard,Ranger,Barbaian
Wizard guild holds
Warlock,Samuri,Bard
Priest Guild holds
Paladin, Monk,Warlock
Dojo holds
Samuri,Ninja,Monk