Re: shift kit
You could run a right side derailleur upside-down, but I don't think it'd work with the big chain for the motor.
Then your rear freewheel would be the wrong way.
Not to mention the motor chain won't work on bike sprockets. So you'd need to change the drive sprocket to a suitable size for a bike chain.
By then, you might as well just get the SBP shifter kit and call it a day I think...