I think that cars should get dirty over time when driving over dirt or mud and get wet when touching water.
I'll have to agree this would be a nice addition but atm i'd rather the BeamNG team work on the new cars that they've been talking about lately and also the many bugs first But this is a great idea!
this would be a great addition especially when you do mud bogging as it is weird when you drive through mud and your truck doesn't get dirty.
I also think water improvement would be great (splashes, collision with cars). It would be cool if vehicles would float for a while before submerging
I dont want it right now. I think the devs should work on the more important things first (more vehicles, maps, physics improvements etc)