One feature I'd like to see is a way to non-interactively edit an existing post. Even the basic minimum — retrieving the most recent post — would be useful. Just to clarify the functionality I'm looking for, here's what I want to do. I have a journal that I use to keep track of certain health stats — number of fluid ounces daily intake. So it would be nice to be able to append to an existing post, so that I can have one post per day, with the entire daily log.
Although I have a specific purpose in mind, I can see many ways where a generalized method of editing an existing post non-interactively could be very useful.