If there opportunity to play with the number of different qualities, then can we introduce and get negative qualities? For example, everything will start with defective black (-10), then rise to low-quality gray (-5) and then only go to vanilla "normal" white (0).
What do you say?
No. This is not how qualities work in the game. The minimum value is 0 = no effect. Moreover, qualities are not random, but always a % chance of a higher/better quality. Not just any quality, including worse ones.