Here is my *working* proposal for beginner-friendliness: the Pd Documents directory. Also includes deken-workingness.
Thanks to Miller for the new "add-to-path" message.
The documents path is an optional beginner-friendly location for patches and externals and defaults to USERHOME/Documents/Pd. If the docs path is not set when Pd is started, the user is prompted about creating it and it can be changed or disabled in the Path preferences dialog. If the user hits Cancel, the docs path functionality is disabled. A subdirectory for externals is also created and is set as the deken install directory. Once set, the docs path becomes the preferred initial directory for file dialogs to help those new to filesystem hierarchy.
Included in this work: deken can now optionally add external directories to the user search paths via a popup after download.