I am looking to create a stylized theme for the progress bar for the batch API screen. I wish to alter the HTML and CSS being displayed in order to do so.
I know how to add the CSS to the page. I am aware of the hook theme_progress_bar, but according to the documentation "Note that the core Batch API uses this only for non-JavaScript batch jobs.".
What is the best method for overriding the HTML for AJAX driven batch API jobs?