Would be fantastic to choose a smartlist have a send date and as people are added to the smartlist they have the email sent out to them even after the scheduled send date. Currently only people up to the send date who are added will get the email. We could put the email campaign on batch mode, set time and frequency and continuously have an email campaign going for that smartlist or tag and now no longer need to do a workflow email. Especially since Email Campaigns has better click tracking with UTM's now.

As you can see in my uploaded photo, it only adds people from tags or smartlists up to the send date and doesn't continue to send emails after the send date.