After much work, and thanks to my employer, there is finally another CSS beautifier in the world. It existed in a broken state before, but now PrettyCSS is actually working. It currently does not do much more than removing invalid structure (just like a web browser would) and complete control over the whitespace. However, this means you can minify your CSS safely with this tool and shrink your CSS files down a bit. It can also pretty print CSS files before you commit them to a repository, ensuring that all of your developers work with one consistent structure.
Next up will be adding tests to the code, better handling of invalid structures, and then starting on property name and value validation.