What limitations for Weapon Attachments exist, exactly? I know you can only take one scope, but could you (Technically) buy multiples of the same attachment? I know it would be nearly irrelevant for most upgrades, (Since nearly all of them just apply some kind of passive buff (For example, it doesn't matter how many extra grips you have, you'll still only be using one,) but I mainly ask because of Exterminators.
Since I'm not reading any technical limitations, is there anything stopping someone from buying like ten Exterminators and building them into a gun? Besides the cost (Just buy a flamer!) and Weight (JUST BUY A FLAMER!)