I don't have all the answers, but I do know this. You can't plug a brushless motor into the 4in1 and expect it to work. Basically, brushed motors are DC and given voltage, they run. But brushless motors are completely different. They have three wires and the ESC pulses the wires in order to make the motor spin. Faster pulses, faster spin. The 4in1 doesn't do that.
So if you add a brushless motor, you have to add an ESC and then you have to get the throttle signal from the 4in1 to the ESC. I don't know how to do that either. Not so helpful this evening.