If you're introducing a variation of an email to do A/B testing on, you have to add it as a random sample choice in the send campaign.
Since this is part of a traffic cop nurturing campaign, you then have to go into appropriate smart lists and add the email there as well to ensure people haven't already received this email.
Then if you have internal alert campaigns where if someone received this email, do this, you have to add it to that smart list as well. The list goes on.
Not sure if this is doable, but it would be nice to be able to select an email, and pull up an inventory of campaigns and underlying smart lists where you could select all of the smart lists that you wanted that one email added to.