I think its great they are getting away with only one gear for simplicity sake and reduced costs and weight. If you look at their power curve for the Roadster, it starts to fall off at 6000rpm. It doesnt end up with lot of power at 14000rpm, so all your accelleration potential is down at 60mph and falls from there. A CVT/IVT is not so much for a gas motor, as it is for any kind of power system WITHOUT constant power. since there is a power peak at 6000rpm, a CVT would allow the full 280HP to be available for acceleration all the way to the max speed potential. (Which is probably in the 170mph range). Part of the confusion I speak of, is that regarding the "Flat" torque curve. This, by definition, means that HP is rising proportional with RPM, it means that even in the lower rpm, accelerative forces are left on the table, not fully utilized. Just think how fast the Tesla Roaster would be if it was constant power, not constant torque! (via use of a CVT, or some sequential, close ratio, auto transmission). I can show you several high performance combusion engine torque curves that look very similar to the electric motor, right up to the point where it redlines. Then, the eletric motor performs its magic.
If Tesla decided to race one of these little gems, It would do very well in the club ranks as is. Picture how light it could be with all the interior gutted. A modification of a second gear would help it with accelerations in areas where it would most be mostly used . (i.e. after 60mph, more like 70 to 120mph). Even if the car only had a 120mph top speed, it would be fine for tracks here in northern california. I bet it would surprise a bunch of racer mainstream.