Would be good to have characteristics for you car i.e traction, cornering, aerodynamics, understeer, oversteer etc like you have with the drivers. As a result developing different areas would effect the car stats i.e increasing development on the front wing would cause more front grip, but results in more oversteer.
Also at the start of each season you can choose a base design direction i.e High Downforce, Balanced, or High Speed each giving you slightly different characteristics for the car, based on the prevous seasons development.