It reminds me a bit of Avatar :P
Well, I always say that all stories can be good stories, it just depends on the one who writes the story (not trying to put you pressure though :P ).
I like the thing of controlling elements, ancient clans and wars between bad guys and good guys. Its always fun to read, besides I like that style very much.
Anyway it seems you have written a good plot. If I was you, I would read all I've written so I'll have the opportunity to change the things I want and have an idea of how the story keep going. I always check the whole story before adding something new, and I always rewrite something xD I'm quite a perfectionist... Btwd do you know ALL that's going to happen in the story and did you think about ALL the characters and names? If you did so, its just a matter of sitting and writing ;)