For the purposes of this demo the sa11y.js plugin is enabled on all internal pages and is accessible to everyone.

My thoughts are that this will only be accessed by authorised users from within the Joomla site administrator by clicking on a new button in the content toolbar. 

joomla content toolbar

When you click on the new Accessibility Check button then a modal window will open showing the current article and with the accessibility checker activated. It will then be easy for you to quickly see any issues and remedy them.

modal window with the Joomla accessibility checker in action

Options

There are very few options and they can all be set whenever the checker is loaded and will be saved until they are next changed.

the options for the accessibility checker

The Rules

All of the rules that this checker covers can be reviewed from the menu on the right. At this time they are the standard rules provided by sa11y.js but it is easy to customise these rules or even to add our own just for Joomla.