[mxstbr]

This is useful for structuring components internally, but sadly doesn't help solve the theming issue at all :-(

What you want from theming is a global skin. You want users of your component library to be able to say "I want all of my buttons to be red" without having to wrap the component or pass a prop to every component. (simplified example)

Doing so just with class names is very very hard. It's what we've done for ElementalUI (together with Less), but it just doesn't work – it's a pita for users!