Tranquility should be separated from punishment to avoid/minimize the stigma of its actual purpose: as a justifiable option for mages who aren't trusted as reliable, but allowing them to take a path short of death. Using it as a punishment changes that already fragile context.
How is it a fragile context? Being forced into tranquility unwillingly is a punishment, you are either being punished for not being trustworthy or not having enough potential to be considered a human being whose opinions should matter in their treatment, which is why you are being given brain damage to make you more useful to the whole. Some people enjoy punishments others would find to be torture, such as bondage fetishes or sadomasochists who enjoy being bound, injured, and psychologically assaulted, and even in some cases strangled, while many others would find such practice appalling if done onto them without their consent.
There exist Qamek, which reduces all individuals exposed to it into mindless laborers. If we are looking at purely economic benefits, I can see no reason that we can't begin forced tranqualization and qamek exposure to individuals who the system either deems to be not worth the dealing with, or who volunteer, and not only begin to make more money on enchantments but find a new source of cost free labor as well. And I say giving that authority to individuals in power and removing the former restrictions, as would need to be done in order to make such an economic system viable, is absolutely the best route to try and improve society.
After all, as long as you don't get on the people bad side, do everything they want, and question nothing, you won't have anything to worry about when it comes to being pressed into having your mind permenantly altered for economically beneficial reasons.