I love where you are going with this.
I think separately most of the pieces are great but there are a few areas where they don't flow together and my eye is stopped. Does that make sense?
The bodice (if thats the right term) is the biggest part that seems a little odd, it totally stops my eye and there I am staring at those lines that lead me to the armpits and not up to the most awesome "illumination" of the collar and In all fairness I can see you aren't finished with it and the waist area... but I really want to say that I'd like to see those horizontal lines go away, maybe change the neckline to be less horizontal and more dynamic... perhaps carry the shape of the reverse scallop thingies that are on the collar. (yep, I know no technical terms, unless "thingy" counts)
I think the back/bottom is great! love the drama of the train and the feathers really bring the fire aspect to it, along with the color.
As someone else said, you might bring the feathers somehow to the front, even if its just a tiny bit for flow.
What seems to be missing is carrying the red up into the top, partially due to the horizontal on the breast and party due to no red.
I don't think it should be heavy however or even extend all the way, just a bridge/fade. Embroidery does sound good, perhaps time consuming though. I like how it goes from the red to the pale and anything heavy might ruin that effect.
I am in love with the collar, I think it fits the theme so much, its like illumination, rays of light shining up from the fire, the pheonix.
I am not a designer, I don't play one on tv, and most days I can't even dress myself to match, so take what I say with a grain of salt and also know that I really really do LOVE what you have done so far and am very impressed.
(I hope that was helpful, you seem like you don't just want the arse-pats but some different eyes looking at it critically)
and umm... please keep us updated! when I saw this my jaw dropped, I can not wait to see the finished results and good luck!