Proposed solution-
A shared Google Doc between owners and moderators is created. In this doc, moderators and owners alike will both log any permanent bans they make-- alongside their name, the reason, and their moderation status (Moderator, Owner)
Permanent bans may only be issued in clear, obvious cases of ToS abuse, and with good justification, or if it is in the best interest of the banned. A kid being 12 3/4 years old is not justified, for example.
Owners will check this doc every other day. They will select the Moderator bans that have not been reviewed, and talk to the moderator about them. If the bans are approved, the approved bans will have (APPROVED) written next to them by the approving owner.
If the ban is not approved, the ban will either be labeled (DISAPPROVED), or will be deleted. A strike will be logged against the offending moderator. Three strikes levies a punishment based upon severity, at two or more owners' discretion.