So,im a Brazilian,so i would love to see a national car,so one suggestion would be the Gurgel BR-800 '88.
It would be a amazing car to represent Brazil,it is a simple hatch,It has a 2 cylinders engine,that pulls 33 HP,but,on the other side,it is very,very light,and can reach 74 mph.
It would be very cool to tune this car and see it reaching 160 mph,like the beetle.
Now,for a american car,i would love to see the Chevy Cobalt SS 2005-2010,sadly none of the horizon games ever seen one of these,only in motorsport.
A car that i also would just LOVE to see returning is the AMC Pacer X '77,sadly it only appeared in one Horizon game.
I like luxurious cars,one of these being the Lincoln Continental Mark IV,with those amazing headlight that look like eyes opening.