It's not a mirror. We already do that. A mirror is the same on both sides. Flipped will swap both sides.

So

If the character has raised an eyebrow when mirrored the figure raises both eye brows

When flipped only the opposite eyebrow is raised.

The smirk swaps sides, the JCM for the other side of the figure.

Yes this is really, mostly for people creating  content. Making a JCM is a big enough pain making one. But, making a symmetrical JCM for the opposite side was nearly impossible. Was. Now you can just flip it.

I'm supposed to have already done a tutorial for this but I keep getting distracted. Stay tuned. There's some limitations and clean up necessary once the flipped morph in created. I'll cover all that.,