If I ram my tractor into a wall, does it mean my repair level is affected in any way?
I suspect the repair level is just a value that decreases with usage. I think it would be much more interesting to keep the repair level but have it impact the probability that your equipment work break in some way. It could be a major breakdown, which would mean it wouldn't work at all, or some kind of minor fault that would have to be fixed eventually. Of course, ramming your tractor into a wall would be a thing that could instantly render it unusable.
