An "accessibility" package has been added to CTAN:

Has anyone tested this?  Is this a possible way forward?

Also, I noted that in this issue comment on Github, Karl Pettersson has noted that the ConTeXt PDF writer produces accessible PDFs:

https://github.com/jgm/pandoc/issues/5409#issuecomment-504438591

That might be helpful for those looking to produce accessible PDFs.

Regards,

Pranesh