does something like this exist or - if not - would there be an interest in such a plugin?
Does not look especially hard to make. Would not even need much of a GUI (assuming it gets the set of charts
to be updated from the current
installation): something that shows last updated timestamp, a frequency selection (e.g. weekly), and perhaps an "update now" button.
One problem might be the legal
aspect of NOAA requiring downloaders to click some buttons but I guess (have to check) that it should be OK if we limit it to updating downloaded charts
because the user already agreed to their conditions once.