Jetpack Related Posts enhancement ideas

I hope some or all of these ideas can be implemented into the Jetpack Related Posts module. tyvm for it.
- [x] ability to use the shortcode anywhere (not just in the loop, but okay to return false if !is_single() )
- [ ] ability to take arguments like size, post_type, has_terms, date_range, exclude_post_ids, and include_post_ids (e.g. force post ID '1875' to be one of the related posts)
- [x] add site-wide settings at the Reading settings for image size, date range, etc.
- [x] auto-inserting of related posts on 'posts' post type shouldn't happen if the shortcode is detected in the post's content
- [ ] ability to disable showing of related posts via wp-admin post editor (i.e. on a per-post level)
- [x] ability to index posts without comments enabled. I believe it should instead look for if the post type is public or if it's publicly queryable
- [ ] add a Related Posts widget

Start by reviewing the Jetpack Related Posts module and the unresolved checklist items in this issue. Narrow the ideas to one independently scoped enhancement, then confirm its expected behavior and completion criteria with the maintainers before implementation.

Written by the indexing model from the issue text.