please explain further what parameter do you want to be controlled via EGP
The master comp has a graphics background, plus two pre comps that contain MOVs of the two different guests on the show. The pre comps contain several layers made up of solids with various transfer modes and masks to add a "look" to the underlying MOV.
I would like to be able to swap out the MOVs of the guests via a template and not have to open AE.
Hope that explains it a little more.
From your description, I wouldn't even fart around with the new, shiny AE Toy. It's just getting in your way.
Just render out your background in AE. Make it a looping background if necessary.
Everything else can be done in PP.