Why not do some 21st century hotrodding? Drop in some more powerful motors. Sure, it'll cut the range but you'll get there twice as fast 
Heck, I'll bet the battery voltage is computer controlled. Hack that and jack the voltage up. Works for a Power Wheel.
Keep the body (where else are you going to get a track car that doesn't need a cage?). Remove the powertrain assembly, and install an Audi V8/016 powertrain!
Keith Tanner wrote: Why not do some 21st century hotrodding? Drop in some more powerful motors. Sure, it'll cut the range but you'll get there twice as fast
Nope, battery voltage is determined by the wiring inside the battery pack. Motor voltage is determined by the controller, and big boy electric motors won't respond well to a simple voltage boost (well, not for long at least).
You could give it more or more powerful motors and controllers, once the battery can handle the power draw and increased heat generation.
But putting a more powerful motor in will actually have very little effect on range if you drive at the same speed, most of the difference might come from the motor being heavier. It mostly just gives you the capability to run down the battery faster.
In reply to Keith Tanner:
I didn't suggest that my plan of action would be very GRM, but if you're going mad on an i3, then you might as well go full on super car mad. Though the money would be much better spent on an LSNDRF.
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