So you sent me a link and I've listened twice now. Here are my very n00bish thoughts:
The piano through 0:50 seems a little muddy, however I think I have a long-term bias against that particular octave, and it always sounds muddy no matter what's going on down there. If I were editing it myself, I'd declutter some of those chords and make it sound smoother and simpler. It happens again for a few seconds at around 4:38, during the part that's from Draco's solo.
The next few minutes, up until the bridge-like part are very pretty, but it seems to build really slowly, especially with the higher intensity and pace of the climax of the song.
Overall, I love the seriousness and simplicity with which you interpreted the original pieces. The strings are nothing short of gorgeous and I think they are very well-mixed - their levels are great and I hope you don't change them. I especially love the jump in volume during the climax, because it kind of reminded me of both the LOtR score (which was awesome as far as I'm concerned) and Samuel Barber's volume-insanity in most of his symphonies, in particular Adagio for Strings.
I LOVED the addition of the chorus at around 5:50, although I really, really wanted it to be more dramatic than it was. I would call it a yearning, even.
Oh, and I totally understand not going into Celes' theme. It's pretty and all, but also overused, and it wrongfully overshadows the other parts of the opera, which you have focused on here with great results.
Okay, so I guess that's all I have so far. I think it's beautiful overall, and I hope it's accepted by the powers that be.