As Titus Brown was kind enough to inform, it turns out that Advogato has an XML-RPC interface. You can read about it here: http://www.advogato.org/xmlrpc.html. Thus, no need for mechanize (thank goodness... that would be been like swatting a fly with an engine block).

I still want to be able to make posts to my diary via email, so I will adopt my old MT/yarn-based script to Advogato's XML-RPC. Nightly exports could be done with either XML-RPC or with urllib... we shall see.

Titus also mentioned that he had more to say on the matter, and an update would be forth coming... I look forward to that :-)