I understand why they aren't our primary weapon (you have ranged attacks, and a knife, would you rather shoot at someone then pull out a knife, or pull out a gun whenever you want to shoot, while running around with a shiv?)
idk about crafting, as I don't have armstech, but I swear I've seen some nice crafting recipes on fan sites
no idea about the "aim" knives, might be for companions or something
a big thing I hate is how no matter what knife you use, it always looks like the same shiv. also the 400 armstech "project lightblade" (saw it on a fansite) SHOULD NOT look like a traditional vibroshiv