Approval for newly created Clients

Good day all,

Is there a way where a newly created client can only be activated once it is approved by a manager? What we want to do is add the domain into "Accepted Domains" so that any client who falls into that domain can register and view the tickets in the Location associated to the domain. The only problem is that anyone can then "guess" a domain and request a user. I know there is a option "Require E-Mail Validation" but a second step in the approval process would add more security to this feature. The only approval flow that I am able to find is for tickets created and not for client creations.

Any suggestions would be appreciated.