Hi AJ (and Optimizing Matters),
Thanks a lot for your feedback!
We are currently developing a new version of the plugin (v3) that will work differently. It will include advanced CSS optimization (PHP based) and concatenation and it will enable to selectively enable HTTP/2 Server Push for concatenated stylesheets or individual stylesheets.
The CSS optimization module contains many unique innovations, such as for example timed CSS loading and rendering. This makes it possible to load and unrender stylesheets based on for example a media query, or when an element scrolls into view.
On a mobile device this will enable to save +100 kb in data-transfer while the same page would load with +100 kb extra stylesheet data on big screens. There are many new abilities with the feature.
To enable professional performance tuning, the debug modus offers a Performance API object with several measure points. Using localStorage enables super fast CSS rendering (250kb CSS in 25ms, faster than the first paint and thus instant without using Critical CSS).

The new plugin will be a package of optimization modules that can be used stand alone or as a selection of modules. Some users were requesting that some of the functionality, such as PWA optimization, would be published as a separate plugin.
WordPress is currently reviewing our advanced Web Font Optimization plugin. Once that plugin is published and tested, the CSS, Javascript, PWA, HTML, Security Header and HTTP/2 optimization modules will be made available. Each plugin will have 100% focus on a aspect of web performance, making it more easy to improve the quality over time.
You can follow the developments on our Github page. A beta of the Web Font Optimization module is available on Github.
https://github.com/o10n-x/