ok , now my suggestions
car:
i like to race with brakes heating simulation (shouldn't be hard to simulate it)
multiplayer:
restrictions set by host (additional mass and reducing engine power)
tracks:
ok, after watching european f1 gp, i think that weather sim is most missing point in LFS, in any other kind of simulations ( flying , sailing ) weather is most important thing. and i dont mean snow ice or any other extreme conditions, just a rain ! set less grip level on tarmac (im not sure how is it on gravel), more brake locking possibility, and good graphic effects to set less visibility. then make it appear randomly on multiplayer hosts and we've got best race simulator ever !
if someone suggested it eariler , sorry, i have no time for reading it :P