One Manual-Activation Membergroup where Site Preference is Self-Activation by Email

We have a site with global preference set to Self-Activation by Email. Now we want to add one member-group, Employers, for which the SuperAdmin will have manual activation. User in that group will have partial permissions to view certain templates until the SuperAdmin does the manual activation.

What is the best way to do this, and also send emails so the user receives email that they have partial permissions and are waiting full activation, then to send a second email that they now have full permissions?

My proposed design is to have the member registration form assign the new user to member-group Employers-Pending when the user clicks the self-activation link in the email. Now when the SuperAdmin goes to ‘View Members’ on CP and double-clicks that new user, the SuperAdmin can click ‘Member Administration’ and change the member-group to Employers.

But generating the emails is the problem. When user clicks the link in the email, the URL has ACT=62, and that triggers method activate_member in mod.user.php. I found the hook member_register_validate_members in mod.user.php which I can use to get the new member’s group_id, and if it equals Employers-Pending, I can send the email.

However, I don’t find any hook for the second task. When SuperAdmin clicks Update on the CP to change the member group, the function administration_update() in cp.myaccount.php is invoked, and there is no hook there.

Any suggestions? Thanks in advance, Aharon