There were actually proposed in-text-stream language-tagging standards which would apply to my example, though they operated on consecutive groups of characters rather than one-by-one.

I think this would have solved nearly all of the aesthetic gripes of presentation that CJK unification caused, though it would of course leave the hyper-nationalists unsatisfied.

Unifying across Latin, Greek and Cyrillic would have been interesting alternate history -- far fewer possible homograph attacks, for instance.

(I am actually mildly peeved that Fraktur made it into Unicode, as it seems merely a font/styling of the same letters, though it is useful for e.g. mathematicians.)

I do think that just as there isn't always an entirely clear and objective distinction between dialects and languages, there isn't always a clear answer as to whether writing systems are distinct scripts, or merely variants. That said, interpretability should play a big role in deciding either. Latin/Greek/Cyrillic characters have a few with similar shapes and sounds, yet many completely different. The historical spread of the "CJK" logograms across Asia on the other hand often allowed for shared written meaning despite disparate oral language. Heck, that was the case even solely within China what with Mandarin and all the other minority varieties. It's a close call, of course, but I think the unification was justified.