…but the more I think about it, the more I like the idea of it looking like the Tome of Battle: Book of Nine Swords in terms of structure.
Ignore the wuxia feel of the book for a moment. What’s the structure of the classes in it?
Well, there are different schools of martial maneuvers maneuvers (let’s genericize these a bit and call them categories of “class abilities”). Each class has access to a few such categories. Some categories are unique to a class. Some overlap. Each class has potentially different rules for how often they can use these class abilities.
Each category has several different types of abilities at different levels. Higher level abilities typically require lower level abilities in the category (unspecified as to which ones) as prerequisites.
I’ve already written about how I think the spell system would be better off in this format… but what about doing all class abilities like this?
A rogue could have access to categories like sneak attack, stealthy movement, trap mastery, etc.
Multiclassing would be taken care of by feats or something that would give you access to a category from another class (including, potentially, a category of spells).
I wouldn’t be shocked if 4e looked something like this. The ‘categories’ here aren’t much different than Star Wars Saga Edition’s (or d20 Modern’s) talent trees, though they are larger.