Does a longer stator equal more torque in a BLDC setup?
In short, yes an increase in active length (stator and rotor) will produce "more torque" for a given operating point.

The size of a motor is determined by the torque it has to deliver. For similar motors with similar cooling systems the motor torque is proportional to the volume of the rotor and hence the overall motor volume.

However... an increase in length will increase the rotor's inertia which may or may not be tolerable for the system.

Increasing the number of turns will also increase the torque production as the number of amp-turns increases. 

Both of these will increase the motor's torque constant Kt, but also the motor voltage constant Ke. This will potentially limit the maximum speed with respect to the inverters voltage source.