Driving a DC motor with a common ground to the negative input it is possible if you only need to drive it in a single direction. Driving the motor through PWM mode works with a single output connected. (same as picture below with only the "U" connector to motor) However the current control is not useable as one of the current shuts is not used, and the watt hours consumed is also unusable. This also disables the safety features of the ESC.
This would also be usefull for driving resistive loads.
The hardware would allow the configuration shown in the diagram with working current sensors, and this would also double the useable current. I don't think this would be too hard to implement, but another motor mode would have to be added called something like "DC Single direction common ground" .
The current code that drives DC motors is viewable here:
The ennoid ESC is used as an example in this diagram