Can we add an approval process/queue to emails sent through CiviCRM?
I'd recommend a different concept - maintain a VIP group and then exclude those group members when you're creating a group to send the mail to (use custom search "Add/Remove Group").

The reasons are:
1) No further development required!
2) If you have to approve each bulk email they receive, they may receive a lot of emails at once. It effectively bypasses any frequency control your staff are producing for the main members.