I have NO IDEA what the person who said you can't layer glasses with earrings, eyelashes, piercings, and tattoos is talking about.
Second of all, CC items that DON'T occupy the same slot are ALREADY layerable. The reason it doesn't exist is that it can't be done with our current knowledge and capabilities. Y'all, first of all, if literally anyone knew how to make multiple CC items which occupy the same slot layerable, it would already be done.