[romwell]

Why not simply augment LaTex with PDF tags which would be inserted manually, in the process of typesetting?

Something like:

    \pdftag{blah}

Common packages could then generate these tags, and very few modifications of TeX source would be needed.

[choeger]

Yeah, one could do that. But then again, one could do that with any other scripting language. A true declarative document would mean a single source of truth and freedom from those technical matters.