de-breath plug-in

Is it possible to add a de-breath plug-in that will clean up narration by removing breathy sounds without further tampering with the signal?

You could try this “Noise Gate” plug-in:
It is a "Nyquist plug-in. Installation instructions for Windows:

Note that if you completely remove breaths, the result can sound quite disturbing (living people breath).

I’m using noise gate to “remove” breaths–de-amplify them.
It took a while to refine the attack and release, because the gate sometimes removed the -ed or -ing of the word preceding the gate.

My settings are:
level reduction: -22
Gate threshold: -15.80
Attack 120.0
Release 707.0

It still leaves in the loud deep breaths, but I edit for them: select and amplify -15.
And I still sound human, but the breaths aren’t distracting.

Of course it depends on the volume of the original recording (I turn mine up to about a -1 before doing the gate). After that I use the compressor with the settings:
threshold: -16
Noise floor: -65
Ratio: 2:1
Attack time .2 seconds
Release time 1 second

And then I’m done. But first, I also use the de-clicker and de-esser. They take some time, but I browse my email and the news while waiting. I’ve got a noisy mouth.

Hope this helps.