Please concider the following:

When a user is creating an email within a record allow them to add saved content/creative to the email.

Maybe a button that is titled "Insert Saved Text" that brings up a window and allows you to select one or multiple selections of saved creative/content/text.

Also, an option to save a email after it has been sent as a template and after saving an opton to share with others.

This along with Attach From Group Docs would be great.