More advanced rules to add users to Organizations Collecting Feedback

It would be nice if users could be added to organizations with more advanced rules than just by looking at email domains. For example we have 2 internal organizations where we can use email domains, but would like to add all other users to a separate organization called "External". I can't find any way to do that today other than manually adding the users. A way to do it could perhaps be to use negation - for example a rule that states that users NOT coming from domain Y and X, should be added to Organization "External".