imagine what would happen if ... the brake discs were replaced with carbon.
This company has been advertising Tesla brake upgrades for some time.
http://www.racingbrake.com/
Although it appears their carbon kit is still pre-order only.
The stock rotors are very heavy, here are the numbers.
Stock Rotors:
29.5 lbs front, 28 lbs rear, 115 lbs total
Two Piece Rotors, Steel Disc, Aluminum Hat: $2,200
22.4 lbs front, 17.4 lbs rear, 79.6 lbs total
35.4 lbs savings, $62 per lb
Carbon Rotors and Big Brake Kit: $15,250
13.5 lbs front, 9.7 lbs rear, 46.4 lbs total
68.6 lbs savings, $222 per lb
(From this company the carbon rotors are only available as a big brake kit upgrade, so new larger calipers are also included in the price.)
The carbon rotors are difficult to justify for that price. The steel two piece look much more reasonable. But I would still be very hesitant to put two piece full floating rotors on a Tesla. I have them on my Elise and they make a bit of noise while driving around. The Tesla is so quiet that the noise could be quite pronounced. I would prefer partial floating to full floating for the Tesla.