It would have been innovative and interesting if James Cameron had made the same film with no white actors. Want to talk about racism? How loud would the screaming have been if the actors had been exclusively East Asia or sub-saharan African? It is doubtful if Cameron could of obtained financing for the film unless he cast whites as the main villians.
It was perfectly fine for Hollywood to cast asians as the evil heavies during the thirties and forties, now it's the turn of the whites. And it's equally racist.
Ironic that you say that, the Cameron film's namesake 'Avatar, the Last Airbender' was a fantasy about 4 Asian "tribes" which were based on Japanese, Chinese, Tibetan and Inuit cultures. The Japanese were war mongers and committed torture and genocide.
To add to the irony, the live action film of Last Airbender is apparently going to use white actors in all the roles.