Somewhere I saw a plot of horsepower available at the wheels vs. speed.
1) Basically from 0 to about 10 mph was a linear ramp set by the max motor current (or max torque, same difference). For all I know it was set by torque limits on the CV joints, but it was clearly torque/current limit linear curve
2) From 10 mph to ~93 mph the curve was pretty flat, tilting down maybe 5-10% where motor windage losses take their toll. The flat was set by the 80 kW motor rating (or some other max power draw limit, possibly max battery current for all I know).
3) At ~93 mph the available power drops suddenly to 0 hp where the software limits the speed to the maximum motor RPM.
Changing to a different gear ratio would either get you more 0-10 mph torque with less top end speed, or less 0-10 mph torque with a higher top speed. Everywhere in the middle is simply limited by the power handling of the motor and changing gear ratios would have no effect.
Given the >90 mph is plenty in the USA and the torque below 10 mph is pretty darn peppy I see nothing compelling about having either a different gear ratio or multiple gear ratios. The acceleration from 30-60 mph is pretty wimpy, but that is a 80 kWh motor limitation, and almost nothing to do with the gear ratio chosen.
I personally would love to see the Leaf 2 have something like 100-120 kW of maximum power with some software settable option to have a softening of the available torque at the lower speeds, say 60-80 kWh available to 20 mph ramping up to full 120 kWh at 50 mph to help minimize undesired excitement.
