We're in the process of optimizing our Jive email template as well, and would love to bubble "Recent Content" to the top. Will you let us know if you found the code to do that?
Also, in addition to the weekly Jive update, our Community sends a monthly "Community Newsletter," to all of our external customers, regardless of their Community status, as well as to Community members who may not currently be customers. Here's an example of our April NL and May NL which we post in our Community NL archive.
Thus far, these newsletters are by far our most effective tool when it comes to driving new Community registrations and participation.
Hope this helps.
All the best,