the only issue that I see as it stands is power. each car would have to have a calculated set of battery packs lined up, to be changed every, say, 10 minutes. the problem is charging. to charge a 4200 pack in 10 minutes you would need some serious cooling. maybe even evaporative (IE a huge heatsink over the cells with a plant sprayer type nozzle squirting mist over it).
although, A123 cells can be charged in 15 mins. the cost then becomes astronomical, but, the only other way of doing it i guess is to use cheap (racer cast-off?) GP3300's, as i know of a person who uses 2 chargers in parallel to charge at 20 amps!
i'd love to see this at my local track. the circuit is perfectly suited to this kind of racing.