That means bumps at every surface change, every crack, every little surface blemish.
That is alot of work, but I thought of something. What if the bumps are not on the mesh? Instead you have a "bump map" that goes ontop, it's writen by texture, so it would be realistic. I'm not talking about bump mapping as in graphics, I'm talking a surface file that goes with the road textures to define the surface of the road physicaly.
Infact, you could even use graphics bump maps now that I think about it, instead of reading the hight for lighting though, it reads if for the physical texture of the track. relief maping already works this way, it builds the surface based on the texture map. The difference is the surface doesn't have to be actualy reliefed by the map, only the simulation needs to know where the bumps are.
The textures would need to be locked, so you can't cheat by changing the surface maps, but it would be worth the loss of moding, it would add realism and the capabilty for the devs to change the road surface easily once its added.
Its just an idea, I don't know how well it would work, if at all. But it would be an inovative and interesting concept to try.