Different stiffness of plastic for pretty much all of the plastic parts. Arms, knuckles, hubs. Have them go from hard (graphite) to soft in three degrees. (Stiff, Medium, Soft.) There is a ability to use EA3 over Graphite, but the EA3 I don't find to be really much softer then the Graphite.
Does anyone make aluminum parts for the car like hubs? It would be nice to use a rigid c-hub when traction is especially high. Increasing durability of some parts would be a nice option also.