I have two ideas that would be great to add as features and then this would really be the super-ultimate plugin for keeping my WP db tidy:
1. Auto-draft clean up
When I run optimization there is still a few auto-draft left in the posts table, which is created by WP. It would be nice to get rid of those as well.
2. Revision control
Now the plugin works as a scheduled or manual but still "on-demand" tool, although it could have a passive feature of not allowing revisions created in the first place. I use now a separate plugin for that (http://wordpress.org/extend/plugins/revision-control/), but that has not been updated for ages, and also does not take care of the postmeta table, only the posts table. With this little extra added to this plugin here, it could steal the show from all else and be the one-stop must-have of WP db caretaking.
(Although I need to add that there is a very nice work done here already, keep it up!)