With a lot of discussions about sensors, interfacing with payloads, and even changing the motor arrangement, what are the capabilities of the current cape? What expansion circuitry would be necessary to add, say, a compass, or a lateral thruster?
not much extra circuitry would be needed, just some wire connecting, and soldering.
the Aux2 output can be adapted to be an extra servo/esc output. And the I2C is available for further expansion. the compass could go on this together with other sensors, since i2c is a bus interface.
there are i2c to servo/esc interfaces that can give up to 16 extra servoes/escs http://playground.arduino.cc//Learning/TLC5940