Make it possible to make a copy of a draft mailing

It would be quite useful to be able to make a copy of a draft mailing. As it stands currently, if you want to duplicate a draft email (for instance, if you want to send two slightly different mailings), you have to send it first and then reuse it.

I'm not sure if this would be complicated or simple to implement (essentially the same as re-using a mailing or something more complex). Does anyone have thoughts?