That's a neat workaround, Brogan. I posted a suggestion relating to this a while ago located here. As that points out, you can also make your Super Mods admins, but via the control panel only and not by changing the usergroup, and removing all but the ban permissions. This still, however, opens the admincp to them, and allows them to view certain aspects which do not have an off switch (like the error log).
IMO, there really is no need for a mod cp, as all moderator functions are performed inline on the forum, and banning a spammer is done through the spam cleaner. As Brogan mentioned, more moderator privileges are planned.