I keep hearing that there is going to be an option at some point. I hope they offer it for the 2005 model year cars so that if I ever want one, it will be legal for stock class autocrossing.
Having said that, if there is one offered I don't think it will help the car as much as an LSD helps many other cars. The Elise has pretty darn good traction as-is. Also, it looks like the front of the car might like more front bar, which also tends to help with corner exit traction issues if any.
