Okay, I need help with this one. I can't think of any reason it shouldn't work, and it actually makes some sense, but I'm concerned about encounters being trivialized.
The campaign that I've been running is about the secret discovery of Cadmium, and soon thereafter its alloy companion by a House Bendott, during the events of The Final Empire. The PCs are in on this secret by now, and have access to a healthy stockpile of Cadmium, and also possess a few non-renewable impure Misting vials of "Bendott's Alloy".
They're expecting a big physical assault soon, and they've come up with a combat application of this Bendott's Alloy that seems extremely potent: they'll have the party Mistborn down some Bendalloy and set up a bubble that contains the quite skilled team Coinshot. Said Coinshot will then fire a massive number of coins at all visible targets, then drop the bubble and watch as they must defend themselves from a massive number of attacks.
He's got Steel 7, which won't be significantly hampered by the effective Bendalloy penalty of 2. Somewhat irritatingly to me, while 20x speed is probably still plenty enough for this feat, the impurity actually seems to work in their favor, used in this manner.
Are there any issues with this that anyone can see? (Please say yes... it seems like it would trivialize most encounters)