if you turn on the cheat: aggressive Traffic the cars on the highway should still drive as fast(or faster) and not slower.
you should be able to get in cabs and let the cabdriver take you somewhere also for busses.
if you tune up your car it should go faster.
you should be able to bey things at the 24/7 like Cigarettes or
beer and use them whenever you want it.
your bike must get dents if you hit anything or a flat tire.
roads must get destoyed by bombs that would be really cool!.
Sorry for the long post.
gta is gonna kick your ase!