Well, move-sets should be ignored for the time being for the Aura. The Aura is more an inate ability, in relation to the ability of the pokemon kinda.
The Aura shouldn't be thought in terms of "moves' but what the pokemon's being stands for. Rayquaza is the titan of the sky, and as I said, weather does not really affect him.
What does Rayquaza do? What does it stand for? What, if anything, does legend say this Pokemon can manipulate? Those questions are could for considering the Aura.
An example of this would be Articuno, who is said to freeze the moisture around it. Thus Articuno creates blizzards with every flap of its wings.
Knowing Articuno can do this, a valid Aura would be the ability to cool the air around it, to possibly freezing temperatures so that the Aura can create "ice" to use.
That is what I want the Aura to be, a simple ability of the Legendary-turned-human, movesets might come later into the RPG, who knows? Starting off however, you only have the Aura.