@eschwartz,
I suspect you're just being being provocative
but wouldn't you say that the Right Tool for the job of exploding/massaging/rebuilding a calibre library epub/azw3 whilst maintaining the integrity of the calibre database may be a calibre container class which already contains most of that functionality. And that a Python package, cssutils, which knows all about css parsing and style rules may be the Right Tool for massaging a css file.
Actually my questions are purely rhetorical, as a rule I've never known any two techies able to agree about much of anything
And on the whole the Right Tool is normally considered to be the one we already know how to use or "if all you have is a hammer, everything looks like a nail".