it would be an extension of an access control list system, the "name" would be a special tag and the posting rule would be "whoever has been designated a delegate to post with this tag"

it would work a bit like a team blog

the actual delegations don't have to be public but probably have to be public, so there would be a public (broadcast) message signifying delegation that would need to be part of what goes out to other places to syndicate it, and internally this could regulate the ACL

i started working on an ACL with similar ideas just for controlling access to the relay 

 and yeah, really, i think communities/groups are probably a more relevant way to do this, the only distinction is the "corporate identity" instead of the user being the top shown author