From Amarok Wiki
I absolutely agree with all of the above. Your use cases are almost identical to mine.
The only other thing I would add is the ability to log in to your amarok backend from a webpage that included the ability to setup playlists and play to some kind of active browser content, like a flash player. That would be amazing.
Also, actually, something else to consider would be plugins to integrate mythtv with amarok, and be able to use the mythtv frontend as an amarok front end as well, so that you could still get your ratings happening but play it through your home media-center (if that's your setup)
Anyway...I was thinking about starting trying to code this up on my own (some kind of fork? I've never actually done this, but I am computer science degree holder), and I was all over the amarok 1.4.x database tonight (had to convert from sqlite to mysql).
Anyway..let me know!