Aren't brushless (& sensorless) motors more like stepper motors? Since they are brushless, you need to handle the phase changes manually. You will need a driver circuit for each of the phases. Slow motor movement can be controlled by shifting power from one phase to the next (by using PWM power techniques.) A microcontroller is only fast enough to manage this power shifting at low speeds. At faster speeds, the processor can shift phases using full power (no PWM.)
Phase changes must be accellerated and deccellerated at rates that can be handled by the power curve of the motor (taking the load and friction into account.)

These are just some thoughts. I have never done this before.

<>< Lance.