Limit current of ESC by software
You are probably overthinking this.

First, as soon a DC motor is rotating, there is an internal voltage source which works against the outer voltage. Second, the rotor coil of a DC motor is fed an AC voltage because of the commutator, which means its inductivity adds a lot of additional resistance to the circuit, depending on speed.

So, overcurrent is only a problem at a standstill and very low speeds. The usual way to handle this is to have thermoswitches at all interesting points (battery too!) and thermofuses as a measure of last resort.