Basically, if there are specific posts from a given set of posts that you DON'T want displayed as part of this plugin, is it possible to add a parameter to exclude one or more arbitrarily specified post IDs?
so, like, exclude_posts='83,106,25,4'
Order of listing unimportant, obviously. Just, if the post IDs are listed in the exclude parameter, it overrides everything else and don't get included. I suppose this would mean that if you wrote post_id='83' exclude_posts='83' it would mean nothing would be added to the page, since exclude would take precedence over include? C'est la vie. The feature would probably be worth the minor quirky situations like that.
Typical use would probably be more like:
[posts-for-page cat_slug='foo' exclude_posts='83,25,19']