Endgame kinda caught this, so he gets credit here.
You can use Streetpass to BUY SKILLS with the same name [err... same character].
Marriage Seals allow you to hop to your partner's classes.
...Kamui gets any and all classes of choice by selection at the start.
Kamui can marry anyone.
Therefore, all characters have a potential access to any class in the game.
Chaining and some Tedium ahead guys--- because if that's the case, on any given run with given enough gold and time, by abusing the ability to buy skills, it'd be possible to get any possible skill combo on any character.