What I was looking at was you could use a small motor, but compensate by having the mechanical advantage of the transmission, so torque wouldn't be an issue.
I think I might not have been clear with my concept. I actually wasn't including an internal combustion engine in this electric car transmission concept. In the last sentence I meant to say "a much smaller motor" meaning an electric motor.
I didn't realize Toyota's Synergy drive had a CVT transmission, so that would be the way to go. I was looking at the Tesla which only has a single fixed gear when I was pondering this idea. I was considering a much less exotic idea for an electric car, where the motor/transmission combination would weigh about the same as the Tesla motor with no transmission. You could have performance if you really needed it without having a high horsepower/short range motor.