There are a couple of things I'd like to see in the next update.
One, Dual headlights for the Golf Mk1. Those look a little bit like an authentic custom touch.
Two, The Mazda RX-7 Veilside bodykit from F&F Tokio Drift. That kit looks so clean and modern. This is also because I don't really like the current bodykits for the RX-7.
Three, Neon lighting. Should've been in the game already, if I'm quite honest. With the current lighting system that would look amazing.
Four, Better brakes in a straight line. In the race Javelin (when you go from full speed high way to a 40 mph 180 degree corner) I noticed it took a really, really long time for me to slow down. Not so much if this was a simulator, but as an arcade game, this felt really out of place.
Other than that, keep the customization options coming. Some cars feel like they don't have really any custom items at all. Although I can understand this being the case for cars like the 458 Italia and the F40, for cars like the Honda S2000 or Nissan 240sx (which are well known for being tuner cars) I think there should be more bumpers, skirts and head- and rear light options.