Andrea, I have had an attempt at using brushless motors for my rover:
https://discuss.ardupilot.org/t/redclaw-crayfish-aquaculture-feeder/50311/11?u=bill_k
As mentioned in this post I had to use an Arduino to convert the RC pulses from the autopilot into the appropriate analog voltage plus reversing signal. It proved to be do-able and had a good outcome in controlling the motor on the bench. I guess it would be relatively simple to add low/medium/high speed control switching to the Arduino functionality.
My problem was the very low braking effect of the brushless motors due to the way the supplied brushless controllers worked. My rover has a low rolling resistance and so when the throttle was reduced quickly, the rover kept going faster that the brushless controller could cope. The controller had a brain fade and wouldn’t pick up control again until everything came to a complete stop. Clearly we couldn’t continue with this.
We have swapped to using brushed motors and hope to get back to troubleshooting and using the brushless motors sometime in the future