A motor has very small tolerances for distance between magnets and coils. So making the size of the motor very large is difficult, even more so if there are blades on it with huge forces.
I think it is quite difficult for someone like me to improve state of the art for motors. An expert will probably be able to select a near optimal design in a short while.
I guess for AWE it is better just to opt for something which is readily available at this point in time.