I did some hacking on the excellent “Extra Info” script from Pedro Lobo. I wouldn’t say I greatly improved it, but I did make a fine mess of the code. My goal was achieved, though: special tags create new files from templates with things like subject, source link, date, etc. all ready to go. Trigger it with FastScripts and you can add extended notes to any task using MindNode, Mindjet MindManager, OmniOutliner, iThoughtsX and nvALT.
I won’t go into a lot of details. Here’s a somewhat hard-to-follow video I shot early this morning (Pedro has a much better one for the original script), and you can find more details on my modifications on GitHub. I’m really putting it out there for others to hack on, but it’s working surprisingly well for me.