My primary usage would be linking items in my Books library to items in my Authors library (each of which has 1 empty book as a place holder) via the Authors table Link field.
The Authors library contains several custom columns e.g. dates and places (google map links) of birth and death, significant others (parents, siblings, offspring, etc), obits, other works, wikiP links, publisher links, quotes, etc, etc.
At the moment the Book->Author->Link field contains calibre:\\show-book\Authors\book-id links, which when clicked initiates a library switch with the placeholder book for the Author current.
If it existed I would replace the show-book links in the Books library Authors Link fields with show-details links, which would eliminate the library switch - as I wrote elsewhere - an inter-library peek.
I would maintain the linkages, like I do know: grab the links from BD panel context menu and paste them wherever. Because its at the Author level it's a 1:1 relationship with the Books library Authors table, so it's a do once operation.
I probably have 5-6 thousand calibre links in my libraries - all of which were obtained from a BD context menu and pasted into Author Links fields or long text link editor dialogues. I would want to maintain that approach. I don't care what the links look like providing I don't have to type ASCII in Hex
If Publishers had a Link Field I would probably have a Publishers library, ditto for a couple of custom columns in my Media and Periodicals libraries. I suspect quite a few users would welcome something similar for Series.
A show-details link would also be useful way to link an item in a calibre library into another application - e.g. a personal journal.
BR