Coordination of mechanical and electrical power in electric drives
In all three cases, we risk not providing the required high torque (which depends on both the current and voltage)


No, torque only depends on current. Voltage only depends on speed. In both cases, less losses.

You can think of a motor as a 'mechanical transformer', maintaining a ratio between torque and current, and between speed and voltage, the ratio of proportionality being the kv value that's often tabulated in motor specifications. It's the same value of k for both ratios. If you increase the turns on your motor winding or increase the field, both values of k change in the same way, to keep the two Mw and IV products the same, less of course losses. Energy balance is always maintained. 

If you want to make a very low speed motor, then the best way is to use gearing, but from an efficiency point of view, not energy balance. Given the physical properties of copper, iron etc, it just turns out to be easier to make a high speed motor than a low speed one.

As the copper losses vary as the current squared, it's easy to let your losses rise excessively by using more current than you expected.