The one thing I can say right now is that you should NOT limit this to monks. In Dragonball, the only three characters I would class as monks are Goku, Krillin, and Roshi. The others are all fighters for the most part. (My reasoning is that most of the character don't have anything even remotely like the monk powers, while those three actually do.)
The biggest point is that Monks must be Lawful, and two of the more powerful Dragonball characters, Piccolo and Vegeta, are OBVIOUSLY Chaotic, or at least Neutral.
Then there are those like Yamcha and Yajirobe who are obviously normal fighters, or maybe something out of Oriental Adventures.
In short, make requirements CHARACTER level, not class level, opening the field to all characters.