Adding brake wear is a very good idea, because it makes driving the stock cars a lot more difficult and you have to resort to more engine braking (without blowing up the transmission offcourse

).
Here are some ideas:
As the heat goes higher, the braking force should go down in lfs.
As the wear continues, so does the travel before any braking takes place (like if there is 5mm wear, the brake only starts working after 5% of travel).
Also while your at it, don't forget about knockback in the braking system.
Here you can see a vid I ripped which explains it.