Do you have plans for some kind of CalDAV sync? I am guessing that this a per blend file tasks list, while that is nice it is not much of a use in a real team environment.
I guess you will need to find a Python lib that can interface with any CalDAV serverm from there you will sync the tasks inside the .blend file back to the CalDAV server.
Couldn’t it be possible to interact with the text editor of the specific file to make and read entries? This way I believe it would not be necessary to dig so deeply since the text is open and saved for each blend file.