Dude, you can start a cup making company: "KHarvey's Cupz" you can specialize in 5.78oz or any other cup size. Until six months from now, you can sell your cupz to anyone in the world to anyone crazy enough to buy them. I bet your standard cup sizes: 8, 12, 16, 20, 24, 36, 42oz will sell the best because that is where the demand is.
After the ban goes into effect, boom, anything over 16oz is illegal. You can still make 5.78oz though! I fail to see what point you are trying to make about not being able to buy a 5.78oz cup being the reason why choice isn't valid.