In your Content model, do something like this:
/**
* Do Moderator Action
*
* @param string $action The action
* @param \IPS\Member|NULL $member The member doing the action (NULL for currently logged in member)
* @param string|NULL $reason Reason (for hides)
* @param bool $immediately Delete Immediately
* @return void
* @throws \OutOfRangeException|\InvalidArgumentException|\RuntimeException
*/
public function modAction( $action, \IPS\Member $member = NULL, $reason = NULL, $immediately = FALSE )
{
if ( $action === 'delete' )
{
$immediately = TRUE;
}
return parent::modAction( $action, $member, $reason, $immediately );
}