I told my players that the mint was suspended after the king's death and that the bank has been retooling the presses to put the queen's face on them. Once the PCs learned that silver coins were the problem, one of them decided to set up a coin exchange in Old Korvosa to promote the queen, and is giving out eleven brand new copper pinch for each silver coins (from any city) that doesn't have the queen's face on it. The bank is aware of the coins being a plague vector and they're only giving out fresh-minted silver coins for the time being.
I think that for the most part this is going to work. The Arkonas will soon hear about it and will provide support in the form of protection. This is real protection, because the Arkonas are pretty upset about the plague and will be hurt by every drug addict who dies. The queen will speak out in support, and won't even mind that much since in actual fact the silver coins are a smoke screen to hide the other ways that the plague is being spread.
Aside from a few rowdies during the period before House Arkona steps in, is there any obvious plot-related elements I should throw at him?