Driving. Just implementation of better car physics is more than enough. So long as you guys put in functioning gearboxes with manual transmission etc. and make it so the top of cars have a collision box (not sure if that's actually what the issue is, but it feels like because the top of cars don't collide with terrain, so modders made it so the car bounces and flips back up) I'm happy. Also, slightly less vicious handling would be nice, especially for gamepad users. I literally moved my thumb an millimetre on my xbox controller, and the car did an instant 90 degree turn.
Just some suggestions, that's all.
Can't wait for the day I drive a nice car from the top to bottom of New Zealand.