In case anyone has any interest or useful comment, I'm working on a personal project to present an additional more 'contact-centric' view of email using Roundcube/Larry as a base.
http://3.bp.blogspot.com/-H8yT_pEawmw/T1yDxEfpwvI/AAAAAAAAACM/iuV9pWESuO4/s1...
If the user keeps the 'folder view' in the left pane then the behaviour is the same as existing Roundcube, i.e. the list of emails appears in top pane and emails are previewed in the bottom pane. But clicking on a 'contact' gives the view in the screenshot above. It's a personal research experiment and partially implemented so far (the 'mail' view includes tabbed folders/contacts, and selecting a contact populates the 'preview' pane, but I haven't yet implemented the contact-centric view of the email list which I'm assuming should be possible using a pre-canned email search).
Nearly all email effort seems to be folder/email/thread based, with 'contact' just an attribute of an email that could be sorted/searched the same as subject or date. 'Contact-centric' email would have 'contact' as a primary object as is an 'email' today, i.e. where you see a reference to one, you can click on it and go to the corresponding item.
The contact-centric approach looks like it has some possibilities and if you've read this far and have any interest, particularly if you're aware of related work elsewhere, then my thoughts-so-far are discussed more fully in a blog:
http://collabtools.blogspot.com/
Cheers Ian