Option to make Workspaces internal only / Seperate requesters on workspace level

We currently have a total of 6 Workspaces - two of which (HR and Finance) are regularly communicating with external addresses.  The rest (and the bulk of agents in the platform) are internal only, and are only communicating with internal, corporate emails.

We are finding it frustrating that all requesters are put into the same “pot” on an account level, and therefore external requesters appear in search agents are either CCing or searching requesters in any workspace.  This leaves it very much open to the possiblity of External requesters being CC’d on internal tickets accidentally.

I would either like to be able to A. seperate out requesters on a worspace level completely - or B - to be able to filter requesters to internal addresses only for specific workspaces that only require internal corporate addresses to be contactable.