Now this is something I like! You've got your eyes on both the good elements for a sprite movie, AND an RPG. That's something extra! I also like the FF-references, pretty dramatic stuff. I'm not sure if really fits with Tails being able to cast magic though. It just doesn't seem like it fits with the canon, know what I'm saying? But that's just a personal opinion.
What I'm a little concerned about is the difficulty of the combat. This is supposed to be a movie foremost, right? While I enjoy beating some more difficult monsters, it might make others turn away from this series if you make it too difficult. Just some advice.
Well, I guess that's it! Keep working on this thing man, it's good!