It would be very helpful to add non-constituent records to an email marketing via web-view. Colleges and Universities also reach out to the community, especially for "Community Events" or "College/University News", and they don't necessarily have the records in the database.
Adding the non-constituents, in general, would be helpful for NXT email functionality. There are a number of idea bank suggestions that all have to same concept in them. Hopefully BB is combining the votes from all of them to see the importance and value of this additional piece for their customers/users.