Before-autoptimize hook?

It there any way I can hook right before autoptimize begins processing header / before it starts processing every CSS file? I want to either replace 3rd party plugin CSS link (it bypasses enqueue_style) with my one in header buffer, or pre-process the file content before minifying in order to get rid of all @import statements inside.

Short story: there is a plugin “amoForms for WordPress” which is heavily built upon CSS @import-s; client would hardly decline to use it, and devs ‘re barely going to change anything. @imports are loaded bypassing WordPress & Autoptimize. It @imports 4 google fonts and a bunch of unminified CSS files this way which makes PageSpeed Insights a little bit unhappy…