It is possible to rename system families, i did it via python as i was doing some duplication/renaming at the same time video on the below tweet will show this.
How i would look at this is that you would get all categories, then check them against if they are in the unused families output(use highlighted node in above post). then you will have two list of placed families and not placed families.
You will need to get the placed element of the others then change its family type to the one you want.
Not placed families is a simple delete then import/create the version you want.