Not really viable on most platforms. And not really the right FAQ.
I am not sure that we are really on a different page. I am aware that i am an advanced user and therefore have higher expectations of the software (Which is why I do exactly what you do and transfer my projects to version 5 libs.)
I simply do not think that the small benefits of doing this is worth the hassle for joe normal (and by extension for newbies).
Do you also transfer footprints to the new library? If not why would the rescue lib be bad news? (The footprints included in the pcb file are nothing more than the rescued symbols. Only the way it is saved is different.)