My first idea is every car have smoke from exhaust. I think it would make the game look better for almost no fps drop

-if you have "potato pc" you could turn it off completly
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
My second idea is that as you drive, your car will get dirty from dirt(offroad and on grass) road/gravel dirty (on road and on gravely road like the one in blackwood ) and brake dust dirty on wheels
it will not be fps killer and it will make the game look better with almost no fps drop cost

(texture over wheels/car may be the way to go it won!t be that hard to do in future i hope )

-If you have "potato pc" you could turn it off completly (maybe not needed)
-You could wash your car in pit stops
-Admin (of the server) could turn it on and off.

#EDIT: If it was alredy sugested i!m very sorry for it

No, racing cars do not have smoke from the exhaust. An engine only smokes when it is poorly tuned or being cold. In racing this doesn't happen, because a poorly tuned engine is a waste to race with.

have you ever seen a car washed during a pitstop?

I don't see point in this.. Why would you wash your car in pits anyways?
When you are racing or driving in general,how can you notice dirty brakes or dust on wheels?
If you wanna dirt or dust on your car,you can easily make skin with it.

Only thing would be nice (when new tire physics is finnaly done) is texture according to tire grip (simmilar to assetto)- If you go on dirt, tires get dusty (just a bit brighter texture)

The 2nd idea is probably for cruise. However, during rallies if mechanics have extra time from fixing their own vehicle at breaks, they indeed will wash car for both aesthetic and reasonable purposes, windscreen for example. ( but that you did knew already )

Smoke from exhaust would be nice on engine damages. Smoke amount depending on damage level