Researchers are used to improve your car, including the quality which is the only thing that you're required to increase to make new cars. You don't need too many designers, unless you really want the design to be finished faster
I think the start and end points should be made clear at the start of each map. The initial wave makes two or three or however many they come out of clear but not the destination if there are 2 or more spots where they aren't coming from. Also, would it be possible to let us click on an enemy unit to see their current stats IE health remaining, armor, etc etc?
 "Idle Car Manager"){kind=icon}
 "Heart of Galaxy Beta"){kind=icon}
 "Command & Control"){kind=icon}