Create an uninstall button - it would delete ALL post meta info that was associated with a key of "mbk_simple_series"
Create a way to rename an entire series. This would take a fair bit of work - since the shortcode inside each post would have to be edited. It's not that easy, but totally doable.
Consider storing all simple_series lists in a single plugin option, rather than in the post meta. This would actually help with speed/efficiency since it would cache the results. This would also make it slightly easier to uninstall.
Consider reducing the number of posts listed in a series list. It could be hidden/revealed via jQuery.
Requires: 3.3 or higher Compatible up to: 3.5.2 Last Updated: 2013-3-2 Downloads: 2,739