Originally Posted by Krystian Galaj
I wonder if it would be possible to abstract the functionality of storing of calibre's files on disk in a separate plugin.
"Possible" - yes - but I strongly doubt it will happen. It's very deeply entwined with the other modules. Plus, most of those who are concerned with the current storage system want to directly access the library, and that can interfere with Calibre's use of its database.
If Kovid makes it easier to access the library directly, there are then going to be complaints when Calibre suddenly, and without warning, changes the filename of an ebook or the directory name in what the user will think of as "the user's library."
I suspect it's more likely that Kovid will make it harder
to access Calibre's library directly instead of easier. Originally, the books in Calibre's library were entirely inaccessible - they were inside the database with the metadata - and I imagine Kovid occasionally regrets making access easier.