Well, such a paradigm shift would come at a great cost, as that would amount to creating a new email client along with its twingled data store.

Right now as is, the email client work has already been done by many worthy agents, in my case the Apple Mail.app.

You are right, however, as this task would require careful thought, particularly in limiting the scope of the project so that it descends from the realm of "would be nice" to "do-able."

Maybe at some time I will become familiar with Java or Cocoa and be able to make sense of the existing opensource apps such as Zoe (Java) and Emila (Cocoa), or better yet, I hope twingle.com would open up their secrets so I could read their Perl source and see what magic is going on.