Carl,
I don't think it will be technically difficult to add department or subject administrators. Mostly UI work to manage the admins and give them views of the classes and a couple lines of code granting privileges when a class is created.
Sloan is not using departments or subjects in any interesting way right now, which is why the UI is not well developed. We only need to assign admin at site-wide or group level. I expect this functionality will grow as other institutions adopt.
I'm interested in the question about being able to have more then one dotlrn instance per server. What is the use case you are trying to solve? Perhaps there is an easier way to solve it.
