If you want to develop a DAAP client, I’d suggest you avoid “reproaching” mt-daapd for not implementing things that aren’t actually part of the DAAP protocol, like modifying the data structures. As much as we love mt-daap on this forum, I think everyone understands that there *are* other DAAP servers out there, and it would be strange to implement features not part of the DAAP spec that Apple implements.
And your second request — to change the whole data structure to spit out the XML file you’ve written — would have the effect of turning your DAAP client into… well, something that doesn’t even support the DAAP protocol.
To me, it sounds like the DAAP protocol isn’t something for you. Maybe write a custom job that has support for modifying the database remotely, and uses a slimmed-down XML stream?
Also, check out the Add-On Software forum — there’s a few web-based (using Flash and Java) clients already in the works.