Features and PlugIns:
These are all GPL licensed plug-ins, but the real question is what would be the best way to install them to experiment, given that as GPL they are all eligible to be included in Sakai's OOTB distribution? See Austin's query above.
1) Accessibility, or a11y Checker. GPL, and thus free to change and free to distribute (aka "copyleft") : https://ckeditor.com/cke4/addon/a11ychecker
2) Bootstrap grid, also GPL: https://ckeditor.com/cke4/addon/btgrid
3) Fontawesome Icons, also GPL, MPL, and therefore free to change and free to distribute. https://ckeditor.com/cke4/addon/ckawesome
4) pasteFromGoogleDoc, also GPL. https://ckeditor.com/cke4/addon/pasteFromGoogleDoc