Multisite within a single site to facilitate admin

This is an invitation for feedback, for or against, on choosing Multisite to divide up what appears to be a single site as far as users are concerned, for the purposes of compartmentalising admin over separate sections.

The context is a single college website which subdivides into individual departments: faculty, fundraising, students, courses, libraries etc. Our objective is make sure that people with admin roles within individual departments cannot extend these privileges across the rest of the site.

We're undecided: instinctively some of us feel that this isn't really a multisite network, and that we should try to solve the problems of context-specific admin in a different way - any thoughts on how to do this would be welcome. Then again, we've never thought of multisite operating in this context, and using it to subdivide a site which appears to the user to be a single whole somehow feels a counter-intuitive although possibly effective way of approaching the issue.

All thoughts and suggestions welcome!