We don't use react, but angularjs. We divide every component into its own module. Like our design mode, the toolbar, the different window object and so on.
Every element has its own css, which sits in the index.html with a command <!-- css build --> and ends in <!-- css endbuild --> (or something like this).
When we build the site, these files get concatenated and minified into one file and this one file gets automatically linked to the index.
So, when we remove a module we don't have to strip these parts off a global css. It's all automatic, just remove it from the index.html and it runs as always.
The good thing about this method is that we have different, changeable css files, but, because of the concatenation, one http request is needed to retrieve the the css file.
James B
The Unix Tiger