If the electronic speed control does not reverse polarity as a function of pulse size, then I will need to use the technique Fritsl used in his wall hugging robot.

http://letsmakerobots.com/node/928

(which seems no longer available)

He cross wired the motor with multiple DPDT relay switches controlled by his PIC. I was going to copy that idea, but then I started believing the story of the magical ESC.