Is there a rule to send an email to users every 6 months or so which they must verify to remain active? This way if an employee has left the account will become deactivated should someone miss it.
To my knowledge there’s no rule template available aimed at a scenario such as the one you describe. That exact flow would also be better handled through a system capable of scheduled jobs, for example, on a given frequency the job would run and review the last time a user has logged in (it could query the Management API). If it went above a threshold the user could be blocked entirely or the email verification flag could be reseted and a new new verification email triggered.
The second possibility above, the one about the repeat of the email verification could indeed be complemented by a rule that would only allow users with verified email addresses to login.