Common practice is to "give admin on the package_id" but what does that mean in practice?
It means someone knowledgable with OpenACS pokes around in the subsite administration pages.
The current packages that have some concept of "partial admin" privileges include
Assessment, Categories, Forums, LORSM.
The question isn't how many packages support this, but what would it take to make the handling of package administrators consistent across the toolkit.
The other question is, what if you have a large site, where there are users who don;t need site wide admin privileges, but only need to manage one package.
It also allows administrators to delgate tasks to other users without giving them permission over everything.
Once we do this, we still need a sane and usable interface to choose a user and add them to the group. That is a another proposal.
