I think that the idea of a 'failure rate' is horrible. Say i have come the whole way to the moon, i have no money left and the moon mission is my last hope. Then when i am landing perfectly, one of the landing legs say 'nope, DIE!!!' after a 1% failure rate, and my craft fall over and explode. That would be really unfair. I say change the effectivety of a piece, like the more you use it, you will get better firerate/fuel-compresion/other.