I've done some pages to try to explore the idea of replacing slides, video, captions, and transcripts with wiki page. For example, see:
To extend this a bit more should this be handled with an <aside> element or <div role="complementary">? of should it be a labeled region?
RCE does not filter out the <aside> for the <div role="complementary"> but Immersive reader does not seem to see these as anything other than ordinary web contents.
Additionally, I do not hear any emphasis when <strong> elements are present nor any announcement of headings.