Even if you figure out how to expolde the aec objects your drawing will still be "infected" and that's why the exporttoautocad command creates a new drawing. There are drawing variables, dictionaries, etc... that will still be drawing, cause object enablers to load, infect other drawings.
If your end goal is to get rid of all the AEC stuff, and not have it affect other drawings, I dont think you have another option than creating a new drawing.
I did what MP already mention, I coded up a routine that takes all .dwg files in folder and batches the exporttoacad command placing them into a folder called "exported".