maybe I’m totally wrong as i don’t know firefly’s internals but I figure it can be pretty safely implemented.
If you have a server extension that says change the (say artist) tag of this song then if there is a tag writter installed that supports this tag for this particular song format then tag writting is done else nothing is changed.
Moreover it’s really an “extra” functionnality and those who don’t trust it can choose not to use it. But maybe again it changes the server’s internals too drastically.
The only thing where I see a difficulty is how to get the user feedback of what happened. I don’t know if the songs listing of a daap share can be “refreshed” without disconnecting/reconnecting. Maybe it’s a client issue.