Personally, I don't see the benefit- if I want to have images in a text, I use a format that supports images, e.g. HTML.
As for the "cover storage", there was talk some time ago about including some storage method for formats that eventually lead to a ticket being created, but I don't know if anyone has put it on any todo list
It wouldn't make sense, in my opinion, to develop a separate storage system for old covers, if we are to get such a system, it should be one system for all the files associated with a book entry.