Kitana Coldfire said:maybe its final evolution uses its developed powers to protect and speed the growth of trees?
Sounds more like something a Grass type would do (to me at least). As for the whole of your second paragraph, I don't feel that's the direction the theme is going in? It says Braixen has the branch as a comfort thing, and it also uses it for attacks. I don't see a forest fire theme or any hint that it cares about forests and trees.
To me it's more like a cat playing with a toy fish. Or someone wearing a symbol on a necklace that represents something they're nostalgic about. (at least, that's the closest comparison I can come up with) EDIT:; Or Farfetch'd with its Leek/Cubone with its bone.
Another Edit: If not a Grass type, then it seems Xerneas would be more about protecting life and speeding the growth of plants?