Well, we already have "Super Admin":
Control Panel » Primary Settings » Advanced Options » Main Administrator User Id? "This is considered your Super Admin. Other admins cannot edit or change this user. All welcome private messages will come from this user."
But you're right, having specific Admin Permissions (like Moderator Permissions) could be nice to fine-tune what some can/can't do. FWIW, though, I can't see needing more than 1-2 Admins anyway. The fewer number of people with CP control the better as far as I'm concerned!
