Second, you'll need a lot of batteries. There was an experiment done a while back, probably in the UK or in Simi-SoCal somewhere, where a Spyder was packed full of batteries.
[EDIT -- found the car: http://www.renewables.com/ElectricSpyder.htm ]
The throttle would be the easy part. Stopping it would require polarity reversal and brakes, if I have it right. Reversing the polarity of a high-torque electric motor would be an experiment I'd like to watch; I have never seen that, outside of an Overhead Door garage door opener pulling on an apparatus-bay door at the firehouse. In that application, the motor has to be stopped before it can be reversed.
Now, though, I'm really curious. I'll do a search of the SciAm archives, and see what I can dig up. I also have a few issues at the house that deal with electromechanical 'future cars' from the mid-90s, and I'll dig those out to see what they said then.
Neat question. If you can make it work, more power to you. I might suggest sending it to Alan for go-kart testing, first. There has got to be a good engineering school somewhere near him in Pennsylvania, dont'cha think?