May I suggest an idea of adding another level of user, such as light users...?

Because currently, for our use case, we're working with client users for users such as sub-contractors who don't need much access to the system but it is not possible to add these users to a team and use a department-wide email to notify everyone in that team and everything has to be set to external and users individually added to task ownership.

Client users are (as they were intended), best used for allowing your client to access their project etc.

I feel there needs to be another level of user that sites between portal user and client user which would make our workflow a little easier.