[volatile666]

Unless you can magically add 6 or 7 IO's with associated hardware to the ESC to handle encoder, step, dir enable, sense I fail to see how you could use it.

Lets say one wanted to use CAN to control it. Then there would be free:
-I2C Data and CLK
-USART RX/TX/CTS
-PWM in

So thats 6 IO free to use. Additionally there still would be 2 free LEDs, thats 2 more IO, and youd still have SWD.
btw, what do you want to sense? For its own current there is already a shunt onboard...