Just to provide an update, we are close to launching a private preview. We are in the final testing stages for this feature. We will have another update in the next few weeks with instructions on how to join the private preview.
We continue evaluating several alternatives to provide full email customization. We are actively working on an alternative.
Unfortunately we do no yet have an ETA.Chris PitPat commented
Please add this feature - also, can we add localization?