Weight distribution things: That's a good idea, actually. Though I think next re-release I'll again make two versions, because as it is now you can do some cool stuff with it.
Different sizes of hands: Interesting idea, but is there any use?
Friction: Possibly.
Tracks: That's, of course, the main point of making a car mod. I just haven't gotten there yet.
wish mod triggers will be appoved. that would solve the track thing. you could easily make it (with mod triggers anyway) to whoever touched the finsih line wins.