I think Iam like everyone else and remember back to my school days when we used to all draw car designs in the back of our text books and argue which was best.
So for me its designing the cars but iam crap starting from scratch so I guess I would need to modify a basic mule shape which will mean plenty of detail options.
Secondly the idea of experimenting with different engine combinations i.e.; petrol vs. diesel and different states of tune, turbo’s or superchargers etc.
An estimated performance graph for each car design with top speed, acceleration and economy etc, like a road test magizine.
Finally comes the business aspect which I prob would eventually get round to after I had designed myself out, so to speak.
See I don’t want much, do I.