This is an interesting idea that I have never heard of before. I can understand how this can be a valuable tool for recycling reclaimed shot, but I don't understand the wheelweights.
My experience with wheelweights is that they are a real mess to work with and need to be pre-processed to clean the filth off of them before they're used for bullet casting. Using wheelweights in a melter is a great way to ruin a bullet pouring furnace in a hurry (this is the voice of experience.)
I also find that wheelweights are kind of expensive, relative to bags of chilled shot.
Are you doing this because you have a mother lode of wheelweights?