Of course all of this begs the question; Why isn’t there a Marine Psyop unit out there?
I don't have the slightest idea why the Corps is lacking in that regard. Maybe it falls along the same lines of why we don't maintain Patriot batteries, or don't have stocks of hovercraft like the ones I saw once at Ft. Story.

Somewhere a staff guy is wrestling with this very subject though, and probably with limited success.

I think what you propose may be the impetus for a joint IO publication, with the USA as the lead agent, much in the same way that the joint CAS pub was developed.

Perhaps a simpler answer is that IO, like so many other supporting fires in the non-kinetic COIN fight, isn't sexy enough, or doesn't have concrete training standards that can form the basis of standardized training.

You are certainly on to something Psyop, and maybe it's time for a broader discussion on the matter with a thread in the Equipment and Capabilities section.