What are the options to request confirmation when sending emails to external contacts?

I guess you only looked at the templates? Simply create a new rule (or even use one of the templates), then add the corresponding conditions, exceptions and actions. Also, don't forget to click the "More options" link at the bottom of the New rule dialog.

In your case, a sample rule might use the "recipient is external" condition, and the action "forward the message for approval". It's just a suggestion though, not sure whether it will fit your needs.