You would gain low-end torque at the expense of torque above ~1350rpm in that scenario.
I guess it depends on where you want to optimize torque. For driveability you would want more midrange torque, which three motors geared the same will provide more of than your solution.
If you shift at the right time, you could get a much nicer torque curve through accel and driving.
Illustration:
green is torque curve with 2.2:1 reduction (ball shifter shift spread) with 3 CIM input
dark blue is your proposed torque curve (2 CIM 1:1 plus 1 CIM 3:1 when torque output from that CIM is >0)
yellow is torque curve with 1:1 reduction (3 CIM 1:1)
http://www.chiefdelphi.com/forums/at...d=13714870 18
Mechanically shifting ends up switching between the green and yellow curves at the intersection (ideally), which will ALWAYS lead to more output torque than the blue curve.
Mechanically shifting is the answer.