I've seen a lot of people on the PC section of the SCC forum, and especially the console side, asking how to remove attachments from guns that they don't like. I've found a way ... unfortunately.
Just got the game today in NZ, and I've been playing most of the day. I got up to the White House, with a reasonable number of upgrades for weapons, and with both the DLC weapons and the collector's edition exclusive code weapons downloaded. And then, at the part where Fisher is entering the White House proper, and the game is saving after the cinematic (the three red goggle lights showing at the top of the screen) ... we had a power cut. Only for a couple of seconds, but it switched the PC off during the save process. And when I restarted the PC and the game, my saves were gone completely. Absolutely freak occurence, that there would be a power cut in the couple seconds it takes the game to save, but hey.
Cutting off the save process part way through seems to have messed up the saves on my PC and on the Ubisoft cloud server, because they were gone, along with everything I had unlocked. The game was as new when I first started it this morning, to the point of having to redownload all unlocked weapons, and all weapons and attachments downloaded during campaign are relocked.
So I've got a few hours replaying pretty much the entire game to reach where I was up to. But more importantly, for those looking for a way to completely wipe the attachments from their guns (maybe remove an ugly reflex sight from a pistol or something similar), I think you could maybe simulate my experience by replaying the campaign, waiting for a save point and while it is saving, pulling the plug from the wall. Should be the same loss of power, and probably the same result.
It's a radical solution for those who want to remove attachments, but I suppose it would let anyone who did want to remove attachments play through the game again and only get the ones they want. At this point, its the only solution I've seen to removing them. And to reassure anyone considering this, anything unlocked via code redemption is still available, and Uplay rewards still appear to be present. So think of this as a way to return to factory settings, so to speak.