First of All, excuse my bad english, i hope You Can read it anyway.
I have ordered a ATV black, and im going to buy the firecore package, i dont know If some of theese suggestions are already implantet, But Else They should be 
The player should be able to play the dvd menu.
You should be able to have different tracks of audio and subs and change in the movie, the movie is created Like that.
I Like the clean look and the Apple feel Like menu, But would Like the option to change the background, the Fanart with the movies.
And it would be great If You click on the movie You could choose play movie Or play trailer. I have alot of trailers to my movie collection, and it would be a Really nice feature. The apple site does contain trailers too, But it Might be difficult to get it to automatic find and play the trailer from There, i dont know.
A’s i Said, i am not sure If You already have theese things yet, But that is what i Really could use, and the main reason till i bought the ATV.
Thanks for your time.