I think you are trying to reinvent slimserver. Or possibly Apache::MP3. Or any one of a number of other tools to do just that.
There is no reason they can’t be used in conjunction with mt-daapd — in fact, I used zina for quite a while, serving up the same mp3 directory via web as I did via mt-daapd.
The thing that doesn’t work with this idea is that the mt-daapd server itself is very stupid. It relies on a smart client. (iTunes). Of the two pieces of software, iTunes is much the harder piece to write.
And if you were going to write a daap “client” that was web managed and stuff, it would be easier just to download slimserver and be done with it.
Just my thoughts.